Let me try and clear some things up for you. Patrick is right in that Beryl is old news... check out
Compiz Fusion... it's the combination of Compiz and Beryl (both are used solely for the purpose of desktop effects.)
Ubuntu (Ubuntu is the operating system (like Windows or Mac OS X)) comes with Compiz Fusion pre-installed so no worries about installation... it's the configuration that can be tricky at times, but often Ubuntu comes with the video drivers you need. If it doesn't work by default we'll need to know what graphics card you have so we can help you install it.
Now, onto the issue about installing on your Windows hard drive... there's two ways to do this... both methods have a little risk involved so you will want to make sure you've backed up all your important data.
One method is repartitioning the drive... from the experience I've had with this I've found it's generally tricky to do this without messing up your windows installation... it's possible (I've done it before) but generally pretty risky. This involves having two separate file systems on your hard drive... one for Windows and one for Ubuntu.
The other method is called
Wubi... this method is very simple... basically it's an installer that installs Ubuntu on the windows partition right next to Windows. Once again, if you try this you'll want to do a full system backup because it could possibly go wrong. I've never tried this method myself, but I've heard good things about it.
Hopefully that clears some things up and doesn't just make it more complicated.
Good luck!