If unplugging USB devices doesn't solve it, start searching the Windows knowledge base and googling for tips on "troubleshooting slow bootup in windows XP". There are a bunch of different diagnostic procedures you can do.

Here's the procedure I'd use in your situation...

1. Assume for the sake of diagnostics that the problem is a SINGLE service or device driver that's causing the computer to boot slowlly.

2. During bootup, press the F8 key as soon as the BIOS is done loading and the OS begins to load from the hard disk. This will give you the windows boot options screen.

3. Choose "Enable Boot Logging" and let it boot. It will start writing every driver load into a log file.

4. Because stupid microsoft doesn't put time-stamps on the lines in the boot log, you have no way of knowing which one of those lines is the slow one unless you do the following....

5. While Windows is booting, you will hear its hard drive working as it loads various things up. When it reaches the point WHERE IT IS SILENT FOR A LONG TIME because there's a failing device driver, press the computer's reset button.

6. Let Windows boot normally this time.

7. Open up c:\windows\ntbtlog.txt and find out where it died.

8. Then start trying to figure out WHY that particular thing died. Perhaps it's just something you can remove.