"k8m80-m7a"
For that motherboard you need an AGP Graphics card.
Buy this:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814161337
OR this:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814125281
They will come with an instruction booklet that will tell you how to install it.
That will give you enough graphics power.
Beyond that your computer could use more RAM (This will give you 25% more RAM and allow your computer to run it in dual channel mode)
http://www.newegg.com/Product/Product.aspx?Item=N82E16820161161
And if you can afford more, that CPU sux
But they don't even sell processors that are compatable with your motherboard anymore. You would have to look for an Athlon 64 on eBay. (used)
To be honest your computer is VERY old and outdated you could spend $300 and get a system that makes your old one look like total cr*p.
The link below is to a $300 computer that would seem like a race between a gocart and a Farrari when compared to your computer.
http://www.pcdirectsource.com/Item.cfm?ID=2622
You would only need to buy a video card and you'd could be in gaming heaven.
To top it all off...
XP is a lighter os than Windows 7
meaning it takes more computing power and system resources to run windows 7 than windows xp.
that leaves less for your games.
Professional opinion:
That repair shop should not have installed windows 7 on such an old and slow computer. Your computer would run much better using Windows 2000.