I recommend isolating if the problem is hardware or software. To do this, see this page on Using System Restore
. Go down about half way to the section "Recovery Console and System Restore from Windows XP boot CD".
If you can boot from the XP Boot CD without problem (before attempting a restore), it is likely XP is corrupt and needs to be rebuilt. If the Boot CD also generates similar BSOD errors, it typically indicates a hardware issue and even a full rebuild may not fix the problem (i.e. you'll need to fix the hardware first).
If the Boot CD is working, I suggest checking/fixing the file system as a first step, although I doubt this will correct the problem (one can hope). See instructions in Using System Restore above. XP's restore options are limited, but you may also have more stable access to Windows and can backup your files using the Boot CD's safe mode.