STOP 0x0000007A or KERNEL_DATA_INPAGE_ERROR
This STOP error has the same underlying cause as 0x77 errors: A page of kernel data was not found in virtual memory (the page file). This might be due to incompatible disk or controller drivers or hardware problems, such as an improperly terminated SCSI device, bad blocks on the hard disk, or a conflict with the BIOS or other firmware on a disk controller. Run the Windows XP Check Disk utility as detailed in "Checking Disks for Errors," page 1237. If the disk manufacturer has a more comprehensive disk utility, use it to do a thorough check of each physical hard disk on the system.
If you don't have access to putting the drive in another computer:
Boot off of an XP disc, press R to enter recovery console, select the windows installation. Type in the admin password (if there isn't one, leave it blank). type in the following (without quotes): "chkdsk /r" and hit enter
If you can slave it in another PC:
Open up My Computer after you have attached it. Right click the drive > Properties > Tools tab > under Error Checking, press Check Now. Check both boxes and hit Start. It will say that it will be run at next reboot. Reboot the PC and let it perform the disk check.
Also, how long did you let the Memtest86+ run for? You're supposed to run it for a minimum of 4 hours (the longer the better).