The c drive is running out of space the single hard disk in the computer is form

Hi:remove as much stuff as you can put what ever you can on to
Cd's and delete anything you don't need. also def-rag every week
and if you can add a bigger drive as a slave and move all
your "stuff" to the slave drive. When you reach a certain
level of no space the system will become unstable

PS:you didn't mention, how bigger is your HDD?
the HDD nowadays is really cheap
later,G

If all else fails you could compress it. But I'd only treat that as a stopgap solution. You really need a bigger hard disk.

Right-click on the disk icon, select "properties" and check the "Compress" checkbox. When prompted, say that you want to compress all subfolders and files also. It will take quite a while to complete, but should increase you disk capacity by 50% or more.

Delete your system restore files. They take 15% of your drive by default. You can also reduce the size your recycle bin takes up.
To clear the files:
Click Start

Right-click on the My Computer icon, and then click Properties

Click the "System Restore" tab

Check "Turn off system restore" or "Turn off system restore on all drives"

Click Apply. The following message appears"You have chosen to turn off System Restore.

If you continue, all existing restore points will be deleted, and you will not be able to track or undo changes to your computer.Do you want to turn off System Restore?" Yes / No

Click Yes.

Click OK

Then re-enable system restore.

Also if you want to stop recycle bin files being saved to your external HD. right-click on the Recycle Bin on your desktop, go to properties and from here you can allocate how much space is reserved on each HD.

c drive with low disk spae is always a problem for many of us, i just thought there are more choices nowadays, rather than only depend on Windows itself. say,

use free disk maintenance software like CCleaner to clean the system: http://www.piriform.com/ccleaner
or get free space from other partition on the same drive with free software: http://www.partition-magic.blogspot.com/