I lost a weekend because of it. It managed to install Grub in a way that not only meant it wasn't accessible, but neither was Windows or anything else. That was Friday night. Sunday night I had my desktop back to the way it was.
I had to move drives around on the controllers (infact leaving out one completely), I tried to Win2K3 rescue process which I would NOT recommend (it basically reinstalls and kills stuff in Windows directorty, it doesn't do much of a rescue) - all to no avail.
I tried Gentoo 2006.0 - that didn't even get through the livecd enough to be interactive. I tried Mandriva - and that ended up being my savour. It wrote enough to actually let me boot in with Mandriva and fiddle with Grub to get Windows booting again.
MSI 875P Neo-FIS2R ... if you have that board and want to duel boot linux on a seperate drive watch out... I think infact it might that the current crop of linux doesn't sit well with the Intel 875 chipset, or ICH5R.
I've done this before by the way, I'm not a complete noobie. I use Gentoo alot at work, and set it up myself on a server. I've tried and installed many different distros on many different boxes. Grub error 21 intermitently (anything intermintent is a bad sign of quality somewhere), then there was error 15 - which is easier (file not found - why not just SAY that instead of "15" or "21"?!). Mandriva installed grub with no load errors, but I had to fiddle with the config to get it to get it using the NT Loader properly.
May be if I had found out about fixmbr sooner I would have just given up on linux. Infact I thought part of the recovery process on the disks includes "inspecting start enviornment" and "inspect boot record" - but it didn't overwrite it.
Whole weekend wasted. Did get out of the flat and do some fun things, and did manage to fix a burnt out bulb behind the dash of the car... and see 5 spitfire circling Calshot on the beach. But at home... rubbish! I even manage to scratch my Win2K3 Server CD... thankfully not fatally. At least I don't think so, I copied all the files off the CD without any error with XCOPY /v, and Nero didn't detect any errors when I made an image of it. Goodness knows how hard / expensive it could be to send it back to MS and get a replacement.