Hello Rikki
You are quite correct, Clock Speed no longer relates to processor speed, and it was started quite a few years ago by Cirus, follow this link which will give you all the information you need. http://www.tomshardware.com/cpu/
The 3 GHz CPU in your Dell will be fine, just upgrade your memory to as much as the Dell will allow. (I recommend 1 GB minimum, ideally 2 GB)
Hope this helps.
BTW. If you require any further help on this subject you can email me directly, (Just click the email link) or if you have Skype you can give me a call, when I am online. My Skype name is: abacusks1
The only thing you have to remember is that I am located on the opposite side of the world to you.

Bill