I have Win XP Professional on my Dell Inspiron 1405 Laptop (320GB HDD, 3GB RAM)

Suddenly C:\Windows directory size is showing as 85GB, but its actual size is 6.65GB only.
System became very slow because of this. Don't know how this remaining space is being occupied? I enabled 'view hidden files' also.. but its showing as 6.65GB for all files, but overall windows folder size is shown as 85GB..

D: and E: drives are shown normal..
I did run spybot and other antispywares & McAfee antivirus softwares etc. but no luck ..

Please help me..