Here are the things:

We really don't deal with that sort of question here, but the computer hardware/software forum has oodles of stickies and suggestions for you.
http://www.modthesims.info/forumdisplay.php?f=563

Please always read forum announcements and stickies before making posts. They will let you know forum rules, as well as other helpful information. As the announcement, "Hey, where should I post my question?" would let you know, this is not the right place to ask computer related questions. Moving to the correct forum..

No, your computer cannot run TS3. If you would like help with upgrading the machine you have or choosing a new one, please have a read through the help stickies here. If you still have any specific questions, let us know.