If you do a repair, you are reinstalling windows over the original installation. Then your old registry is merged with the new registry so your shortcuts, settings and programs remain intact (mostly. I have seen some losses, but they are usually not severe.) It sounds like your upgrading your cpu, which probably means your replacing the motherboard. If this is the case, do as bonestonne suggests about backing up, then format the drive and do a completly fresh install. Never try to save the old os when replacing the mb. However, if your just upgrading the cpu wothout replacing the mb, I wouldn't worry about it. I have never had a prob with just putting in a faster proc. Finally, when you have finished reinstalling all of your software, making any tweaks, it's all just as you want it, run disk cleanup then defrag. Then use Ghost or other imaging software to make an image. Then, whenever you want, it's easy to roll your computer back to its pristine, just installed condition.