Took infected machine to the shop to fix as at this point my disk management skills are a bit thin. stayed with the tech to watch ... infected 320Gb disk had 3 partitions. From what I can remember the tech deleted partitions C, D & E then created one 100Gb partition & began the installation & to me it looked like only the first 100Gb of the drive was getting formatted. question is, as the new OS installed in the new C partition, did the remaining 200 Gb get formatted & wiped. what's going on on the disk at this stage of the procedure? would viruses get left behind? isn't it best to format the entire disk before installing etc ... ? Do i need to format the disk first then reinstall?