For some immediate space gain, delete all but the most recent Java version & update from 'Add or Remove Programs' (see 'Control Panel'> Add or Remove...)
and see CCleaner settings below.
One disk performance item is to 'compress contents' and 'allow index service'. These help optimize file recovery speed & save disk space.
Start> my computer> right click 'c' drive> properties> general tab: here check both boxes & 'OK'.
Don't freak out: it may say days or more to run, but this time drops dramatically as the process advances. Just walk away and let 'er run for the duration: it will self close when done.
Depending on the files & sizes, it may take several hours to do (maybe do it at night before bed?).
When done, run 'CCleaner' (http://www.filehippo.com/download_ccleaner/)
& defrag the drive.
Once every 3 months run the 'disk check' which will look for physical problems on Hard Drive disk sectors.
For XP do this: Start> my computer> right click 'c' drive> properties> tools> error check: here check both boxes, then OK. The next time you cold boot your system, this process will run (maybe 30-60 minutes) fixing disk errors(if any).
Run CCelaner:
To keep a Windows system running at peak efficiency, registry cleaning is one important procedure (among many others).
Download; create a 'Restore Point; install CCleaner; then:
On the main CC window, the 'paintbrush' tab is for the Windows components that you can clean; (in the 'Advanced' heading, check 'Hotfix uninstallers' to clear these files) & tick the bottom right box (Run Cleaner) an it will delete (or overwrite option) those files.
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Same procedure for the 'applications' tab.
Next, down from the' paintbrush' is the 'Registry' icon (like a Rubik's Cube); first tick 'Scan for issues' button on the bottom; wait for the process to run.
it'll show a long list of entries for the first couple of cleanings; (Back up your first couple of registry cleanings, and if your unit gets ungovernable, restore those files. I've never had to do it, so I can't tell you how. After that the cleanings will be for empty folders or other junk so backup likely won't be necessary).
When ready, tick the 'Fix Selected entries' and CC will take care of those.
For your 1st few uses, have checked the 'show prompt to back up registry files'; open CC> Options> Advanced> check the 'show prompt...' box; then tick the 'yes' or confirm to back up the registry. (It gets saved to the 'c' drive, as 'ccxxxxxx')
Find 'CCleaner' here: http://www.ccleaner.com/