take a look at this link:
http://support.microsoft.com/default.aspx?scid=http://support.microsoft.com:80/support/kb/articles/q265/8/79.asp&NoWebContent=1

Stop 0xC2 or BAD_POOL_CALLER
The Stop 0xC2 message indicates that a kernel-mode process or driver incorrectly attempted to perform memory operations in the following ways:

By allocating a memory pool size of zero bytes.
By allocating a memory pool that does not exist.
By attempting to free a memory pool that is already free.
By allocating or freeing a memory pool at an IRQL that was too high.
This Stop message is typically due to a faulty driver or software.

Possible Resolutions:

A Stop 0xC2 messages might occur after installing a faulty device driver, system service, or firmware. If a Stop message lists a driver by name, disable, remove, or roll back the driver to correct the problem. If disabling or removing drivers resolves the issues, contact the manufacturer about a possible update. Using updated software is especially important for multimedia applications, antivirus scanners, DVD playback, and CD mastering tools.
A Stop 0xC2 messages might also be due to failing or defective hardware. If a Stop message points to a category of devices (such as disk controllers, for example), try removing or replacing the hardware to determine if it is causing the problem.
If you encounter a Stop 0xC2 message while upgrading to Windows XP, the problem might be due to an incompatible driver, system service, virus scanner, or backup. To avoid problems while upgrading, simplify your hardware configuration and remove all third-party device drivers and system services (including virus scanners) prior to running setup. After you have successfully installed Windows XP, contact the hardware manufacturer to obtain compatible updates.

Computer with ATI RAGE FURY MAXX Video Adapter Stops Responding After Upgrade to Windows XP
http://support.microsoft.com/default.aspx?scid=kb;en-us;Q307151

"STOP 0x000000c2" Error Message Appears on a Blue Screen After You Install IomegaWare
http://support.microsoft.com/default.aspx?scid=kb;en-us;Q309155

Stop Error When You Upgrade from Windows 2000: Bad_Pool_Caller 0xC2
http://support.microsoft.com/default.aspx?scid=kb;en-us;Q310527

File Transfer - Old Drive to New Drive
http://www.pcmech.com/show/harddrive/52/

Visit the following URL and perform the instructions to resolve the issue :

http://support.microsoft.com/default.aspx?scid=KB;EN-US;Q307545&fr=1

To get into the Recovery Console, please select the Option Recovery Console after booting with an XP Installation CD. You can also boot into Recovery Console using the Startup Disks for Windows XP. To create Windows XP bootable disk visit the following URL :

http://download.microsoft.com/download/WinXPHome/Install/310994/WIN98MeXP/EN-US/WinXP_EN_HOM_BF.EXE

>>If windows is completely dead is there some way to at least get data off the hard disk?

Slave the disk with another system and backup the data. Then run Windows XP Clean install (not repair)


Windows XP Clean Install Guide:

http://www.michaelstevenstech.com/cleanxpinstall.html
http://theeldergeek.com/xp_home_install_-_graphic.htm 

This one I got from CrazyOne, I think....:)

Try using ERD commander if you can't get in to the recovery console

start the Windows Recovery Console, use any of the following methods:
Start your computer by using the Windows Setup floppy disks or the Windows CD-ROM. At the "Welcome to Setup" screen, press F10 or press R to repair, and start the Windows Recovery Console. From here do something like the following. Or if the file system is FAT32 you can use a Win98 bootdisk to do this. www.bootdisk.com 

copy c:\Windows\repair\TheParticularHive C:\Windows\system32\config
This will replace the registry hive to the last time that hive was backed up. Hopefully you didn't backup the registry at the time the problems started to happen.

Following is a list of the files that are the registry hives. I would suggest starting with the SYSTEM hive and then reboot and if the problem still persists do the SOFTWARE hive next. Note these files don't have a file extension on them

DEFAULT
SAM
SECURITY
SOFTWARE
SYSTEM

For the SYSTEM hive you could try the following before doing the copy method.

ren c:\windows\system32\config\SYSTEM SYSTEM.bak
ren c:\windows\system32\config\SYSTEM.alt SYSTEM

I would suggest to first backup or rename these hives from the C:\Windows\system32\config\ to folder of your making or choice just don't back them up to the C:\Windows\repair\ folder.  

You will probably need to reapply any services patches that you have previously installed.