Chkdsk cannot run because the volume is in the use by another process

Asha22,
It appears from your last post that the reason chkdsk did not run on restart and gave you an invalid error is that you did not put a space between the volume number and the /f.  The correct syntax is:

chkdsk c: /f

You can also run the disk utility this way:
http://windowshelp.microsoft.com/Windows/en-US/Help/bc1393cf-9f9c-79c7-0f91-9337c2c41f811033.mspx

1.  Open Computer by clicking the Start button, and then clicking Computer.
 
2.  Right-click the hard disk drive that you want to check, and then click Properties.
 
3.  Click the Tools tab, and then, under Error-checking, click Check Now.  If you are prompted for an administrator password or confirmation, type the password or provide confirmation.

To automatically repair problems with files and folders that the scan detects, select Automatically fix file system errors. Otherwise, the disk check will simply report problems but not fix them.

To perform a thorough disk check, select Scan for and attempt recovery of bad sectors. This scan attempts to find and repair physical errors on the hard disk itself, and it can take much longer to complete.

To check for both file errors and physical errors, select both Automatically fix file system errors and Scan for and attempt recovery of bad sectors.
 
4.  Click Start.
 
Depending upon the size of your hard disk, this may take several minutes. For best results, don't use your computer for any other tasks while it's checking for errors.

Note: If you select Automatically fix file system errors for a disk that is in use (for example, the partition that contains Windows), you'll be prompted to reschedule the disk check for the next time you restart your computer.

The reason it says the disk is in use by another process is because it is in use by the operating system (Vista) and that is why it has to be run at startup, before the operating system fully loads.

Another utility you need to run is the System File Checker, if you can get your computer to boot, either normally or in Safe Mode.
To run the System File Checker tool, follow these steps:
Click Start, and then type cmd in the Start Search box.
Right-click cmd in the Programs list, and then click Run as administrator.
If you are prompted for an administrator password or confirmation, type your password or click Continue
At the command prompt, type the following line, and then press ENTER:
sfc /scannow
When the scan is complete, test to see whether the issue that you are experiencing is resolved.

Let us know what these tests find and how we can provide further assistance.
Thank you,