Yeah 7a errors are common with ram faults and bad blocks on your hard disk
Download and burn
memtest86 to cd and boot from that allow to test the ram (free test is fine)
Check error reports. Right click my computer manage then event viewer look in system for hard drive errors.
Goto start then run type cmd and hit enter. In the black box type chkdsk c: /r it will say drive is in use check next boot click yes then reboot and go out while it checks