Hi
Equis have announced that Metastock prior to version 8 is not compatible with Windows XP and they have therefore stopped providing support for Metastocks of said versions.
I understand that there are some here that have used MS6-7 for a number of years on XP without a hitch but suddenly experiencing crashes. As mentioned before the program is expected to be unstable on XP.
The only long term solutions is to upgrade to a later version either MS v10 (for XP) or MS v10.1 (for Vista).
A short term solution (that has worked for a small number of people) is to reinstall MS7.02. I call this a "jackpot solution" as some have tried to reinstall it about 6 times before it got running again. You might want to go down that path.
I hope this helps.