Depends on what is the cause. In your case, I would suggest clean install
(even though I always lean toward upgrades) and install W2K as well and
troubleshoot the differences (if this is due to specific software,etc).
Good luck!
How to Install W2K to its own partition. Use a 98 Startup disk and run
WINNT.EXE from the I386 directory. After 2K is installed, boot with the XP
CD and at the Setup/Repair screen, choose Repair. In Recovery Console, use
the following commands:
1) FIXBOOT, answer Yes
2) CD \
3) ATTRIB -H NTLDR
4) ATTRIB -S NTLDR
5) ATTRIB -R NTLDR
6) ATTRIB -H NTDETECT.COM
7) ATTRIB -S NTDETEC.COM
8) ATTRIB -R NTDETECT.COM
9) COPY X:\I386\NTLDR C:\
10) COPY X:\I386\NTDETECT.COM C:\
In Steps 9 and 10, X is the letter of your CD-Rom drive.
How to Install W2K to its Own Partition after installing XP
http://www.dougknox.com/xp/tips/xp_repair_2k.htm