After a bit of experimenting I got per-pixel alpha to work on my Mobility Radeon 7500 at a decent speed. I now present to you, Leddy's guide to per-pixel on older laptops:

This procedure has been executed on an ASUS L3800 laptop.
It should work at any resolution, but my native is 1400x1050 and therefore I can't guarantee that it works at any resolution higher than that.

1. Get your original driver disc that came with your laptop. Install the drivers that came with it (unless you never updated your drivers).
If you don't have them, here are the ones that came with mine (I place no guarantee that they'll work on yours)

http://www.leddyonline.net/repository/winxpradeon7500oem.rar

2. Restart your computer like it asks you to afterwards. Your computer may black screen for a while before login if you have a USB disk attached. If that happens just wait- get yourself a coffee or something like that.

3. Once you log in you'll notice that hardware support for per-pixel alpha is enabled. Have fun dragging around those transparent border windows (remember, you have to select the glass theme BEFORE you get these)

4. Once you've had your initial fun you'll notice that these borders make your computer damn slow. Now proceed to step 5 to rectify this issue.

5. Now, go into Display Properties --> (Tab) Settings --> (Button) Advanced --> Troubleshoot. On the slider, move it once slot to the left. Under it, it should be labeled "Disable cursor and bitmap accelerations. Use this setting........"

6. Click OK. Your monitor will flicker. After that, close all your display properties windows.

7. Your per-pixel hardware support is now disabled, and your CPU is now emulating all the calls. This should be much faster.

PS. This disables hardware support for Constant alpha blending. WindowBlinds doesn't use this, though.

That's all there is to it!