If she likes to color, you can download TuxPaint for free. You can also add your own "sheets & stamps" for her to use. That was a big hit with my son. They have pretty good, simple answers in the help/faq section of how to and where to put stuff.
Also, the disney magic artist studio is pretty cool, but maybe after she has had some practice with the computer in general.
Also, we like iSpy.
I found many games on Amazon for less than $5. You might also try half.com. It's cheaper than most stores.
If you need something really basic, there is Alphababy. I have it on my mac. I think it's available for pc, but not positive. It is also free. The child can use any key on the keyboard without destruction to your hard drive. There are options in the preferences to show letters, numbers, shapes, alternate in pictures from iPhoto/folder, sounds can be added. It's fun for them for a first "game".