i have a computer that pauses (freezes) when doing tasks, until the tower is tapped. Any ideas?

Something is loose.

Power down and unplug the computer from the wall. Open the side of the case and grab on to bare metal to discharge any static in your body. Touch bare metal frequently.

Press on every connection, card, and RAM module to ensure the connection is secure. Check both ends of every cable. Clean out all the dust and dirt while in there - remembering to touch bare metal. Make sure all the fans spin freely.

Check all the cables in the back of the computer.

If still a problem, we will need more details about the computer, operating system, and more details of the problem. Only when hot? Many times a day? Do you lose data when it happens? Any errors in Event Viewer? How long has this been happening? Any recent hardware/software changes?

loose connection was my first thought also, this is a friend's computer, so i've not had a chance to look at it yet, but i wanted to get some other ideas before i went and looked at it.

once i get a chance to look at it myself, and check all of the connection, if it still does it, i'll post more details.