hmmm... ok well i also use the xbox wireless controller (wonderful controller btw, best I've used, very impressed), with an imac, under Windows 7 under bootcamp.
Here's what I suggest. First, make sure you have installed the (latest version of) the xbox 360 controller software from the relevant microsoft site, and reboot. I'm presuming you've done that already?
Of course it's worth just checking bootcamp and windows are fully up to date as well.
Oh also make sure the batteries in your controller are good - if it works with your acer then I presume they are.
Now when you say "wont connect", what does that mean exactly? With mine, once the driver software is installed and everything, I plug in the USB dongle thingy, then press the big grey "X" button on the controller, and the four green lights cycle around in a circle pattern for a second or two, and then it stops on one light, and I think Windows throws a "connected" type message as well. Are you saying, you just get circling green lights indefinitely?
I can tell you, in hardware terms, it definitely works. So there must be something up on the software end.
Hope you figure it out!