Try deleting all the files in your temp folders they will be located here:
First go to My Computer->Tools/View->Folder Options->View tab and make sure that 'Show hidden files and folders' is enabled. Also make sure that Display the contents of System Folders' is checked. Remember to reset these when done.
Your temp folders they will be located here:
C:\Documents and Settings\user-name\Local Settings\Temporary Internet Files\Content.IE5
C:\Documents and Settings\user-name\Local Settings\Temp
C:\WINDOWS\Temp
Then empty your recycle bin and reboot
You could also reduce the amount of programs running at startup