Does anyone here know any good free software for playing DVDs that I can download off the web?

I know there's usually one comes bundled in windows XP, but while I was doing a custom install on windows and getting rid of all the unnecessary shite that Acer likes to add on, I must've un-clicked the DVD player software as well.

All I need is a simple thing that lets me stop/pause/play etc., and doesn't hog too much stuff on the system.

There's no inbuilt windows DVD player.
Most suppliers do a deal with one of the bigger software suppliers to give you a basic version of their software.
There's no legal free DVD player software.

There are some free players, like the KMPlayer and VideoLan,
but their legality is arguable / semi shady.

I'll send you on some links if you want to be a pirate

The two most popular are Cyberlink's PowerDVD and Corel's WinDVD.

Download VLC media player. It's free, simple and it literally plays anything. Dvdx, avi, mpeg etc. VLC media player - Open Source Multimedia Framework and Player