multi(0)disk(0)rdisk(0)partition(2)\WINDOWS\system32\DRIVERS\isapnp.sys

Maybe someday the XP forums "Ask a question " dialog will ask these questions automatically when a new thread is started so I do not have to ask them every single time.  It might even be possible to resolve an issue in a single reply when enough information is provided.

Please provide additional information about your system:

What is your system make and model?

What is your XP Version and Service Pack?

Describe your current antivirus and anti malware situation:  McAfee, Symantec, Norton, Spybot, AVG, Avira!, MSE, Panda, Trend Micro, CA, Defender, ZoneAlarm, PC Tools, Comodo, etc.

Was the issue preceded by a power interruption, aborted restart, or improper shutdown?  (this includes plug pulling, power buttons, removing the battery, etc.)

Does the afflicted system have a working CD/DVD drive?

Do you have a genuine bootable XP installation CD (this is not the same as any Recovery CDs that came with your system)?

That symptom often means your system is afflicted with malicious software. 

If you choose to boot in Safe Mode, and the last thing you see on the screen looks something like this:

multi(0)disk(0)rdisk(0)partition(1)\WINDOWS\system32\DRIVERS\isapnp.sys

If your system hangs in Safe Mode on the isapnp.sys file, you need to look for a driver file of zero bytes in length in the following folder:

c:\windows\system32\drivers

Of course you are going to have to boot the system on something in order to access the hard disk to check for the suspicious file and get rid of it.

If you have no genuine bootable XP installation CD from which to boot into the XP Recovery Console or are not sure what kind of bootable CDs you have, make a bootable XP Recovery Console CD or a Hiren's Boot CD and be sure. 

There is no XP media required to make either a bootable XP Recovery Console or a Hiren's Boot CD.  Then you can access the folder and check to see if there is such a suspicious file and take action.

Once you are booted on the CD of your choice, navigate to the following folder (assuming XP is installed on your C volume):

c:\windows\system32\drivers

If you are in the XP Recovery Console, issue the following command while in the c:\windows\system32\drivers folder:

dir  *.sys

The files will scroll by one screen at a time.  Look at the list of files with the .sys extensions and their lengths.  You don't need to worry about the Directories...  If you see a file(s) with a .sys extension that is zero bytes, that is the one to suspect.

If you are using the Mini XP Mode of a Hiren's boot CD (which operates just like the XP desktop), just navigate to the folder from the My Computer desktop icon and locates the suspicious file(s).

You will want to actually delete the suspicious file once you get running and have run some scans for malicious software, but if you are not sure what the suspicious file is or if it might be needed, just rename the suspicious file for the time being in case you are not sure.

For example, if you found that the zigxrtml.sys file had a length of zero bytes, rename it:

rename zigxrtml.sys   zigxrtml.bad

Renaming or deleting the suspicious file to get the system running is not fixing the problem.  It is fixing the symptom of the problem.

The problem is your system is infected with malicious software and you must still follow up with some scans to remove the infection.

Once your system is running, follow up with MBAM and SAS to be sure the affliction has really been removed.

Reduce the chances of malicious software by running some scans. 

Do, or do not. There is no try.

I decided to save up points for a new puppy instead of a pony!