Can't log in to one of two user accounts, suggestions?

Hello,

I am running Windows XP on our home desktop. There are two accounts we use, one has Microsoft Office and several other applications installed that we use regularly, and the other just has some basic things like a browser, etc. Well about six weeks ago when I attempted to log in to the primary account, it simply didn't let me log in. We have been using the second account to use the browser and check email, but it's a real pain to not have all of our applications and everything when we log in.

Does anybody have any troubleshooting tips for this issue? We have tried a system restore to no avail, and I'm not sure what to do specifically.

Any tips on where to start would be great. This is my parents' PC and the problem first showed up for them so I don't have all the specific details.

Thanks!