I tried doing exactly what you are trying to do with my new system, and all hell broke loose. I had a PIII 450 system with a 440BX mobo and I swapped those out for an A7V133 and an athlon 1.2. The system booted fine with the old hard drive, but that's about all it would do. The CD-ROM wouldn't show up, the sound card didn't work, and the video card drivers wouldn't work either. I tried for hours and hours to sort things out, but eventually gave up. I had another hard drive already, so I just dumped all the stuff I needed on to it, reformatted, and reinstalled windows 98SE fresh. When I did that, everything went perfectly fine. But this was just my expierence. I would suggest you try it the easy way first, and if things just aren't working out, go the format and reinstall route.