I need a cheap, simple midi keyboard for simple recording stuff. I'm thinking about a Behringer UMX25, any thoughts? Also, I only have an internal Realtek soundcard thang, should I get a better one or will it do?

I'd suggest not buying Behringer products unless that's literally all you can afford. In general they have poor build quality and unimpressive signal to noise issues.

If you can spend a little more it's worth getting something by Evolution, ESI, Edirol, M-Audio or even Korg if you find a cheaper one that you like. These will all last longer and work better than cheaper alternatives.

I'm not sure about your sound card, if it has a MIDI in/out then it should be fine. The main thing will be processor speed and the amount of RAM you have.

Any recent MIDI keyboard has an USB connectivity option, so it's completely soundcard independent - you don't need a MIDI port in your computer anymore. Everything controlled by such keyboard should work on your Realtek chip as well - just install universal ASIO driver on your computer for low latencies. Of course using proper soundcard (aka "soundinterface") with it's own ASIO drivers could bring you a bit better results like lower latencies, better signal to noise ratio and stuff.

I think I share Greg's view on Behringers stuff, it's pretty well known manufacturer of cheap and not very reliable stuff

the M-AUDIO keyrig 49 is great. Feels great and lasts a long time. We use them in school.