Star menu-> All Programs-> Accessories-> System Tools-> Disk Cleanup
Disk Cleanup will take you through the steps on how to clean up your temporary files. As you can see from the above image, I had over 7.4 GB in temporary files. This is an easy way to take care of this problem. The other way to do so is to go through your browser. You have to open up the Preferences or Options menu. Once you have it open, find the Privacy tab and push the button to clear out all of your cookies or temporary Internet files. This will delete all of the temporary files that are generated by your browser.
The other way of doing this is to navigate to the following folder in Windows Explorer:
Windows doesn't like you messing about in these folders, but you can just get there if you've got administrative privileges on your own machine. Once there, you can delete all of the temporary files. If some of them are currently being used, Windows won't let you delete them.
Then you can go to this folder:
You can repeat the process, but usually, if you've run the Disk Cleanup utility, these folders will be already almost empty. Depending on how often you do this per year, you can salvage quite a bit of disk space, as you've seen in my example.