I have a decent PC too, custom designed by me for gaming, but with a Creative XFi Elite Sound Card in it for recording, and to be honest I feel like I am as close to industry standard as I want to be. I use Cubase for recording, and for monitors I use a set of Shure 440s.
I believe to use ProTools with a PC, you need a ProTools approved audio card by M-audio too. And in the end, I read around the place that M-audio is laggy for VST effects anyway, not sure if that is true on the high end cards.
Instead of ProTools, I use Cubase SX for PC. With my soundcard I can record at 96KHz 24 bit which isn't quite 192KHz I know, but still very decent. I set the Creative ASIO from 1ms to 2ms to avoid a crackle sound, however I can not hear any lag at all. I had to change it to audio recording mode though (rather than gaming or entertainment mode), so the signal processing time dropped from that of a normal sound card down to 2ms too, was faster on 96KHz than 44KHz too. However I can't hear any lag when I play directly into Amplitube or other VST effects. The best part is the number of channels that I can load with VST effects before the CPU and RAM start to raise. I am let wondering myself what is so special with Macs and those M-audio cards to be honest.
For monitors, it depends on your use. Becareful buying unnessessary gear. I use a set of "closed" headphones for monitoring while recording, so no spill from the backing track ends up on the next track, which is important for editing later. And for mixing, the Shure 440s are referenced and have a flat response so fine there too. I just record one instrument at a time direct into the Creative Elite's DI Guitar input and record clean while monitoring with VST distortion and efftects. Then I mix down the track later with effects on once I have decided on the effects that I want. Alternatively I use my SM-57 on my amp, and directly into an mic channel. If I need to record a few instruments at the same time, I use my mixer and a few headsets, just running the mixer output either to USB or into my sound card. Actually that is where my sound card falls down, or PCs and Windows really, as you can only select one input at a time, but a mixer solves that. However unless you are all in seperate rooms, so no spill ends on other tracks, one channel at a time is fine. Hope that helps anyway, or at least save you some cash buying a studio package if you just want to record your band
Oh yeah you might want to fix the Vista thing. Real time recording is "said" to be best in XP, and worst in Vista too (I guess with the virtualisation part, it runs an OS inside an OS like Vmware to protect itself - don't quote me on that though lol). I just made a multiboot XP x86 partition on my Win7 x64 system, however careful installing XP after later OS's, you need to know about PCs and editing boot files and things. 64 Bit can be problematic too, however they are starting to provide better x64 support though which is awesome.