every time i start my pc OS selection window appears.... even my pc have sigle OS (windows 7)

thanx for reply

but, i am still facing problem. on the boot tab it has only one OS in list. and i cant chage timeout value to '0' . because its asking for " must be 3 or more than 3 "

still need help.....!

What Jeeped suggested will not work in this case since the Boot Manager, which is what you see in the picture, and the boot files work differently in Windows 7 than in Windows XP. Its being present is independent of msconfig settings.

The most probable cause would be that you installed to:

1. A HDD that had another OS on it and was not property formatted and wiped. 

2. You installed to a HDD that had more than on OS previously installed

Either way the result is the same. The install is

1. seeing boot manager files that thinks there is another OS partition

or

2. maybe there actually is another OS partition or some phantom files left over froma previous OS installed.

When Windows 7 installs it will look for other OS's and if seen, it will install its Boot Manager. What you are seeing is Windows 7 BM and the entry labeled 'Earlier Version of Windows' is indicative of Windows XP being on the disk, as when Windows 7 installs and see this other OS, it always labels it as such ... the generic name 'Earlier Version of Windows' instead of calling it what it realy is, Windows XP. It would do this also if it would see Windows 2000 or 98 but I would think or assume it was an OS that old hiding on disk.

Sounds like it is a phantom OS that you can't see or don't know about. In this case I would do a low level format of the HDD and install again.

If that doesn't work a 3rd party tool called easybcd works well for changing settings and disabling Windows BM's as well as Linux Grub BM.

···
In this case I would do a low level format of the HDD and install again.

@Richman101;

Are you seriously recommending a low-level HDD format and complete O/S reinstallation in order to get rid of a 3 second delay in boot sequence?

Sounds like cracking walnuts with a sledgehammer to me.

@raghavendra.l;

Preamble: I started to write out these instructions and then realized that I cannot complete them without further information from you. If you feel that you can enumerate and then delete the rogue entry(ies) then proceed. However, it this is not crystal clear to you, enumerate the entries and paste the output back here and I will try to complete the directions.

Only proceed with these directions if you are confident that you can complete them competently. As mentioned below the first thing you should do is backup the current state of the BCD. It all this is true and you still want to get rid of the three second delay on bootup, then proceed.

This sounds like a job for the command line BCDEDIT.EXE utility. Open a command prompt with elevated permissions using the following directions.

Click Start or tap the Windows key and type c·m·d then hit Ctlr+Shift+Enter. This is the equivalent of using Runs as administrator to open a command prompt. Acknowledge any UAC confirmations and supply credentials if required. This will give you the elevated permissions you will need to properly run BCDEDIT.EXE.

With the command prompt open, type the following command,

BCDEDIT /?

Follow with Enter and this gives you the command help for BCDEDIT.

C:\>BCDEDIT /?

BCDEDIT - Boot Configuration Data Store Editor

The Bcdedit.exe command-line tool modifies the boot configuration data store.
The boot configuration data store contains boot configuration parameters and
controls how the operating system is booted. These parameters were previously
in the Boot.ini file (in BIOS-based operating systems) or in the nonvolatile
RAM entries (in Extensible Firmware Interface-based operating systems). You can
use Bcdedit.exe to add, delete, edit, and append entries in the boot
configuration data store.

For detailed command and option information, type bcdedit.exe /? <command>. For
example, to display detailed information about the /createstore command, type:

     bcdedit.exe /? /createstore

For an alphabetical list of topics in this help file, run "bcdedit /? TOPICS".

Commands that operate on a store
================================
/createstore    Creates a new and empty boot configuration data store.
/export         Exports the contents of the system store to a file. This file
                can be used later to restore the state of the system store.
/import         Restores the state of the system store using a backup file
                created with the /export command.
/sysstore       Sets the system store device (only affects EFI systems, does
                not persist across reboots, and is only used in cases where
                the system store device is ambiguous).

Commands that operate on entries in a store
===========================================
/copy           Makes copies of entries in the store.
/create         Creates new entries in the store.
/delete         Deletes entries from the store.
/mirror         Creates mirror of entries in the store.

Run bcdedit /? ID for information about identifiers used by these commands.

Commands that operate on entry options
======================================
/deletevalue    Deletes entry options from the store.
/set            Sets entry option values in the store.

Run bcdedit /? TYPES for a list of datatypes used by these commands.
Run bcdedit /? FORMATS for a list of valid data formats.

Commands that control output
============================
/enum           Lists entries in the store.
/v              Command-line option that displays entry identifiers in full,
                rather than using names for well-known identifiers.
                Use /v by itself as a command to display entry identifiers
                in full for the ACTIVE type.

Running "bcdedit" by itself is equivalent to running "bcdedit /enum ACTIVE".

Commands that control the boot manager
======================================
/bootsequence   Sets the one-time boot sequence for the boot manager.
/default        Sets the default entry that the boot manager will use.
/displayorder   Sets the order in which the boot manager displays the
                multiboot menu.
/timeout        Sets the boot manager time-out value.
/toolsdisplayorder  Sets the order in which the boot manager displays
                    the tools menu.

Commands that control Emergency Management Services for a boot application
==========================================================================
/bootems        Enables or disables Emergency Management Services
                for a boot application.
/ems            Enables or disables Emergency Management Services for an
                operating system entry.
/emssettings    Sets the global Emergency Management Services parameters.

Command that control debugging
==============================
/bootdebug      Enables or disables boot debugging for a boot application.
/dbgsettings    Sets the global debugger parameters.
/debug          Enables or disables kernel debugging for an operating system
                entry.
/hypervisorsettings  Sets the hypervisor parameters.

You will want to start with the following command.

BCDEDIT /export "c:\My_Old_BCD"

Follow with Enter and you will create a backup of your BCD entries in c;\. Remember that you can use

BCDEDIT /import "c:\My_Old_BCD"

... to restore the file if things go sideways.

All of the BCD entries are identified by GUIDs. You will have to enumerate them before you can start to use other commands on them.

BCDEDIT /enum

You may be able to complete the deletion of the rogue entries using this information. If not, copy it and paste it back here and I will try to help you complete the operation.

More information can be found at:

BCDEdit Command-Line Options (Standard 7 SP1)

Boot Configuration Data in Windows Vista