Well I use the computer to run some programs (like matlab, maple,...) as well as surfing,...
The rpoblem is that it is quite slower than my laptop (latitude D620, 2.00 ghz core due) with the same cache size. I have done disk cleanup, and defrag. with having any acceptable results.
Now depending on which Dell Optiplex 745 you have. Do you know if you have the mini tower or the Small Form Factor or the Ultra Small Form Factor. If you have the mini tower you can put in a Intel Core 2 Quad Q6600 or Q6700.