At TekBusters we clean a lot of computers. Ones that started off nice and shiny and fast and are now going slower and slower. As well as removing malware and blowing out the case we also delete old files and run a disk defragment (see here for how to defragment a hard drive).

Sometimes though even after we delete temporary files the disk defragment wont run as there is not enough free disk space, well it will run but miss a lot of files. Disk defragmenter needs at least 15% free space to run properly. To free up space on XP you might consider disabling System Restore.

System Restore remembers changes you made to your computer so you can restore it to an earlier known good point. This is useful if you install some software that crashes your system. You can then restore your computer to how it was before you installed the dodgy software.

So is this safe? Yes, if your PC is running well. Once you have your updates installed and cleaned out temporary files, ran virus scans etc then reboot. Make sure your PC is running well. Now you can disable System Restore and run defragment. After the defragment you can enable system restore again (though you could use the option to use less space). Since you have checked that your PC is good up to this point, now when you restore it will go back to how it is now.

To access System Restore in XP click on Start -> All Programs -> Accessories -> System Tools -> System Restore