Really simple fix; assuming you're using Windows XP SP2. Basically with the update to SP2, it deletes a file that's required for the compatibility of some older applications and causes this particular subsystem error.
Packard Bell (a major OEM PC retailer in the UK) have a fix for it on their website:
Don't worry if your computer isn't a Packard Bell. All it does is replace the missing file/s removed by Microsoft. The worst that can happen is that it has no effect. Give it a try.