Run ScanDisk -- preferably from a DOS boot. If this doesn't solve it, boot
to Safe Mode and try -- if it then works, you know you didn't really have
everything closed and you can troubleshoot from there. If still no relief,
see Ron Badour's article:
http://home.satx.rr.com/badour/html/defrag.html

--
Jim Eshelman, MS-MVP Windows
http://aumha.org/
http://forum.aumha.org/

Did you find this newsgroup on the web? A newsreader like Outlook Express
will make your online life a lot easier. Get better help!
See: http://aumha.org/win4/supp1b.htm and
http://support.microsoft.com/support/news/howto/default.asp

Have a look here, by MS MVP Ron Badour:
http://home.satx.rr.com/badour/html/scandisk.html
and
http://home.satx.rr.com/badour/html/defrag.html

One option is to reboot into Safe Mode, and then run Defrag there.

Here is a little utility to automate closing all running processes and then running the utilities for you:
GEODisk by MS MVP George Gedye
http://www.it-mate.co.uk/downloads/setupGD.exe
or
http://www.it-mate.co.uk/downloads/GEODisk.zip
or
ftp://12.107.147.141/GEODisk