Doesn't matter, files can become fragmented anyway. Try a defrag if you haven't already done so in the past month or 2.
Get CCleaner - http://www.ccleaner.com Run that with all your browsers closed and it will clear out a load of Temporary internet files, form data, browsing history, cookies, download history so if you, for instance click 'remember me' when you log in to a website when you go there after running ccleaner you will be logged out as the cookies will be gone. But there will be a significant speed increase if you have a lot of junk to clear out.
And as n!ck said, post the log file :)

