If you don't use Skype, you should. It is a fantastic communication device. But my experience with the newest release has not been good. I have a Pentium 4 with 2.8 Ghz processor and 1 gig of RAM. Skype 3.8 works great, but Skype 4.0 had huge delays between when I clicked "call" and when it actually started dialling. I actually sat here for a minute and 20 seconds one time. 3.8 is instantaneous.
I also am not sure I like the new layout of 4.0 -- it is substantially different from 3.8.
Currently you can still download 3.8 for a little longer from: