How does the Dell Optiplex handle gaming?

Happy Holidays! I recently obtained a Dell Optiplex 745 (745LP-2.8PD-8-1T-CMB-7P64) for my son, and was wondering how well it handles gaming? Here are some of the specs:

Processor: Intel Pentium D (2.80ghz)
Ram: 8GB
Hard Drive: 1 TB
with Windows 7 Pro.

He was looking to play games like Minecraft, Flash Games, Portal, TF2, Euro Truck Simulator, Incredipede, Kerbal Space Program, etc.
He also uses Stencyl alot.

By the way, finding out the most advanced game it can play smoothly would be fine.

It's not the computers hardware that matters, it's the operating system that counts the most. M$ is NOT the only computer operating system in the world, Though where you live it is the only operating system you know of, The worlds fastest operating system is Free to download It has over 43,600 Free application software packages, and over 1,800 Free games. You and your son will benefit more from using this free operating systems than you will using windows 7.

Here are some websites to visit that will give you some insight into this free operating system please take the time to visit them and find out the things that you should know but don't

Worlds top IT companies that develop and support this free operating system
http://linuxfoundation.org/about/members

Free Education System that will take your sons education through High School/Collage/ University
http://uberstudent.org

the latest up to date gaming news
http://gamingonlinux.com

For the latest December free operating system
http://distrowatch.com

For the 43.600 free application software and 1,800 free games
http://sourceforge.net/...eforge.net

You can still run W7 if you want to by do a dual boot system