The process is very simple and done in a matter of seconds. Press Windows Pause (Break) and click on the Advanced tab. Click the Environment Variables button on the bottom and another window opens showing all variables. The important ones for use are the TMP and TEMP user variables.

Create a new directory manually on another hard drive, for instance f:\temp. Mark the first variable now and select edit from the menu and change the default location to f:\temp. Edit the second variable in the same way and click on ok. You should restart your computer afterwards.

You could then delete the old temporary directories because they just waste a lot of disk space.