When you are having trouble getting IIS to do what you need, David Wang offers some advice for IIS6 Troubleshooting. Unfortunately in one respect, David’s advice is impractical. The developer faced with an IIS problem in the first instance needs to try and resolve the problem ASAP, and cannot count on outside help. This leads to destroying the state the David (rightly) wants to preserve.
There is another excellent solution - use VMware. With VMware you can snapshot the system state, or clone an entire new virtual machine. Either operation takes seconds. When you have a problem using IIS, and your test installation is running in a VMware virtual machine, you can exactly preserve the state of the “machine” using a clone or a snapshot. You can then figure out the problem on your own (as is usually necessary), while preserving state others might need to look at later.