I have been using a Pentium III Dell laptop as a desktop replacement while my other PC is being repaird. I have noticed that after about 30 minutes of use, on the bottom, where the RAM is, it is extremly hot. Also, my programs will freeze and Windows will lock up, so I just turn it off and come back in 10 mintues and the same thing happens. There is one small fan on the back of it. What else can I do to help cool it down? Is there something that I can put underneath it? I am using it on a desk and not taking it anywhere.

You could prop up the back of it to allow air to flow underneath it. I know they sell laptop incline coolers, but you can just use 2 small things to prop it up a little bit. That should help quite a bit, as it isn't going to keep getting trapped underneath it.