is shortage of memory also known as RAM which stands for Random Access Memory, this is the one piece of info you omitted to include.
To find out how much you have, right click on My Computer and choose Properties.
In the box that opens tell us what it says under the heading Computer:
I have a demension 8400 with windows xp pro media center. It has a 3 ghz processor 160gb hard drive. I have it on a wireless setup. I don't know much about the inside of a computer so I need help. It is extremely slow to open 1/2 hour or so and even more so to get into any program or internet. Yesterday I checked everything I could check and somehow or another I found a screen that had appeared stating errors and saying something about images not being able to open. The computer at times sounds like it is processing something and then it becomes quite again. Like surges. Any help anyone can give is appreciated. I you need more info I will try to find it.