You could Google for a specification e.g. http://www.ehow.com/facts_7292128_ibm-aptiva-specifications.html
or you could probably right-click on the My Computer icon and click on Properties.
You could use a free tool like Belarc Advisor to tell you the spec.
What are you trying to do with the PC? It's too old and slow to access the web safely. Many websites (including chess.com) are too modern to fully work with such old systems.
Artfizz, Thankyou for taking the time to answer and help me. Just a note that it is not my computer and belongs to a friend who is not on the internet and dosen't want to get on it for his own reasons. He asked me if I could find out the rating. He plays it at home over and over and is just wondering.
Is it the rating of an old CHESS program on the PC that your friend is interested in? Or the speed/performance of the machine itself in general terms?
Well, which chess software is he running?
Can anyone tell me how to find a rating or an estimate of a rating on an old IBM Aptiva with a "Bios Date" of Dec. 1997. It Originally had a "Windows 95" but later was updated to "windows 98". I am sorry I don't know anything else about it and am just trying to help a friend.