It seems impossible, I am shocked.
I installed Windows 7 on my PC, it took about 30-40 minutes to install, and normal boot (when there's no program installed) takes me about 30 seconds. I run a VM on the same PC, installed the same Windows on VM and installation took me about 20 minutes (!) and it boots in 10-15 seconds every single time.
I noticed smtg like that when I did the same with Windows XP (about a year ago) but I thought it was a mistake.
I wouldn't believe in it too, but the fact is - now I'm writing my question from that PC.
So my question is - How is it possible?
Note 1: On host machine I used ISO image to install and installed it without DVD or USB, so DVD and USB couldn't cause performance loss.
Note 2: I am running Windows 7, VMWare Workstation 9, VM has fixed-size VMDK (15GB) and uses my both processor cores.