In my experience a STOP 0x7E error is usually caused many different things.
See this link:
http://aumha.org/a/stop.php#0x7e
The parameters in the ( ) 's are significant.
The first one states that the error occurred while accessing memory.
The other 3 refer to memory locations particular to that crash. More info
is available in the Help file of the Windows Debugging Tools.
Presuming that the Windows 98 installation was not infected, then I'd
suspect that it's due to an outdated driver on the system. But, were there
any problems that caused you to upgrade to XP?
I would suggest backing up all your data to external media (disks or drives)
and perform a clean install of XP using the upgrade disk. This will require
that you have a copy of the Windows 98 installation media. Just boot from
the Windows XP CD and install it normally, erasing the old Windows 98.
During the process it'll ask for the qualifying media - that's when you'll
insert your Windows 98 CD.
Good luck!
- John