Nice easy to follow instructions thanks guys: 
1: download the file slmgr.zip (links below)  
 
2: make a backup of C:\windows\system32\slmgr.vbs (in case the keygen works, replace it back with the original)  
 
3: use slmgr.vbs from the zip-file to replace the one in C:\windows\system32\. If you have problems with permissions, select file...goto properties....take ownership....then change permissions.  
 
4: write down your partial or entire productkey. You can check your key with "magic jellybean" (from our pack)  
 
5: goto Start > Run, type "cmd" and OK. Now type "C:\windows\system32\slmgr.vbs -ipk generate". A process called "wscript.exe" will start and can take quite a lot of CPU resources. It will check aprox. 10000 keys per 30 minutes.  
 
6: now the waiting begins. It can take very very very long before you get some results  
 
7: after some time (hours, days) check your productkey with "magic jellybean" again to see if it has changed  
 
8: if your serial has changed try to activate Vista by going to Start > Run. Now type the command "C:\windows\system32\slmgr.vbs -ato"