Before you start that clean install you may what to do the following:
Use Windows Disk Cleanup to free up drive space.
For a more thorough clean up take a look at CCleaner as a tool to remove
Internet history info, cookies, temp files, auto complete and other junk. In
the 'Windows' tab listing check the item types you want deleted.
Also available is customization, see Options/Custom to add any
other/additional folders you want files deleted from.
http://www.ccleaner.com/
To free up your CPU you might what to disable unneeded services:
See:
http://www.theeldergeek.com/services_guide.htm
or
http://www.beemerworld.com/tips/servicesxp.htm
Also there may be some sub-process or application that's taking all
the CPU resources and slowing down your PC.
To locate/identify these processes try Process Explorer:
http://www.microsoft.com/technet/sysinternals/SystemInformation/ProcessExplorer.mspx
Once you have Process Explorer installed and running:
In the taskbar select View and check 'Show Process Tree' and 'Show Lower
Pane' options.
Then expand the process named 'Explorer' (click on the + sign)
In the column on the left named 'CPU', look for any high CPU usage.
Next click on the CPU column to sort the processes by %CPU usage (Highest to
Lowest).
Then click on the process that's using most or all the CPU % to highlight
it,
Now that it's highlighted, right click and from the options listed select:
Search Online
This should display what out there on the web about that process.
You can also double click on any process to open up a more detailed
'Properties' window.
Note: some entries like Explorer and System/Services may need to be expanded
to show the detail,
(sub processes), in this case click on the + located to the left of the
entry.
JS