I assume that you are talking about Internet cache. If so, go to Interet Options in the Control Panel. Use the Settings button in the Temporary Internet Files to select where you want the cache files to go. To reclaim the space, be sure to deletethe old location.
If you are talking about the system swap file, Select System in the Control Panel. Select the Performance tab, then select Virtual Memory. Again, you can select the location you would like the swap file. You will need to reboot after this change.
I've change both, and have never had any problems with it. Both (or either) of these changes is a good idea if you have two physical drives as this may reduce activity on your system drive.
Hope this helps!