Indeed, I pressed the update-button too fast. I liked the untethered boot of SP 0.71 a lot better. Where can I find the 0.71 version?
The latest 0.7.2 version still supports an untethered jailbreak of iOS 4.2.1 (option + click 'Create IPSW' and select the iOS 4.2.1 IPSW). However, to restore using this version you will need to have your SHSH blobs backed up.
This should be made clearer. Perhaps by adding an options menu in the windows installer?
I was looking for this solution for hours and it was right infront of me. I just had to press left shift to choose my IPSW.