Can I have IIS 6 & IIS 7 on same system ?
>> 1 OS - NO
or I use 2 OS on 1 pc - is this possible to have IIS 6 on one & IIS 7 on second ?
>> Yes - dual or multiboot or get virtualization software to run addtional OS on top of another
What is the best way to upgrade if IIS 6 ? Is IIS 7 is compatible with XP
>> Only XP x64 built in with IIS 6, others are IIS 5.1
Best way recommended is clean installation.
IIS 7 won't run on XP, yet you can install IIS 7 Manager to manager IIS 7 from XP machine.