Gallery Suddenly broken - What''s the first thing to do?

The following information is required to get an answer:
Get this information from the PHP diagnostic (in the configuration wizard).
Gallery URL (optional but very useful):
Gallery version: 2.2
Apache version: 1.3.37 (Unix)
PHP version (don't just say PHP 4, please):4.4.4
Graphics Toolkit: NetPBM Graphics Toolkit
Operating system: Windows XP
Web browser/version (if applicable):

My Gallery was working just fine.
It stopped working today.
I can see the homepage, but that's about it. I don't see any thumbnails.
If I click on the link to the album, I get 404 error page.

I am going to re-install the program...
Is there something I can do before re-installing the program?

Thank you