New OS install on infected disk

[Freddy]

Hi everyone.

Got a batch of infections on 2 computers connected via the router so took machine1 to the shop to fix as at this point my disk management skills are a bit thin. I stayed with the tech to observe his actions & learn what I could at the session & after leaving the shop with the 'fixed' disk decided I'd be better off in the long run learning how to format, backup & copy volumes, reinstall, restore & generally manage multiple hard disks on different computers myself & get as independent as possible.

The infected disk in question had 3 partitions. From what I can remember the tech removed partitions C, D & E then created one 100 Gb partition & began the installation.

My question is, as the new OS installed in the new C partition, did the remaining 200 Gb get formatted & wiped. Would someone please explain what's going on on the disk at this stage of the procedure? Would viruses get left behind? Isn't it better to format the entire disk before installing etc ... ?

Much appreciated

[Freddy]

Second question if I may ...

One computer is ASUS motherboard, the other is ZOTAC.

The ZOTAC is a new installation, never been online, all ZOTAC drivers already installed, all working (XP SP3)

Can the following be done ... use the ZOTAC disk image, restore it to a new HDD then run that HDD in the ASUS machine then overwrite the ZOTAC drivers using the ASUS disks? or am i asking for problems?

Cheers

[Freddy]

PS I realize I may well be in the wrong forum entirely.

If so please ignore me. OTOH as a lowly newbie all advice on above queries will be accepted with gratitude.

Regards.