Well, before we do anything else I reckon we should install a more up to date version of FF2 so
click here and download the
2.0.0.15pre.en-US.win32.installer.exe version of what is there to your computer and then install it over the top of your existing version which should be in your C:\Program Files folder. I don't see much point in doing a clean install yet.
Let's see if that improves your performance.