I started out with Mandrake. Mandrake 10 is very good for newbies. The install is easy, and it comes with a lot of the software needed to get going. If the machine you are putting it on is of decent speed (>1ghz, 128mb RAM) it should run it fine. Most of the distros that are user-friendly are pretty hefty on they system (Red Hat, Mandrake, etc). The one problem I found with Mandrake was I didn't find any dependency/software solver. Basically, most of the software you download needs another library that you have to download. That library may need another piece of software...etc. With Mandrake you have to get all that and install it manually, with Debian and Slackware a lot of it is done for you. This only pertains if you need to install additional software though...
Now that I've gone way overboard, I'll just say...go with Mandrake. But remember...Linux is not Windows. It will take time to get used to it. I found installing things to be the hardest to get used to since you can't just click on some setup app...its all text-based
That is...unless you use a package manager. But that is another post
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