After spending hours and hours with how to install Windows 8 on Parallels correctly, I have a solution. here is the full story: I used Bootcamp to Install Windows 7 x64 on my Bootcamp partition. Worked well. then I purchased the windows 8 upgrade for 30 EUR, for the installation options I chose: USB-stick. I was then able to install Windows 8 on my bootcamp partition. Tried it, liked it! Then I got Parallels 8. Wanted to convert the bootcamp partition with the Parallels transport agent, but that PVM did not boot. So I added a new PVM in Parallels and installed Windows 8 using the USB-stick. Worked, but I was not able to compress the virtual HDD, nor could I change its size afterwards. It always said that the file system is corrupt bla bla (yes I tried many things like chkdsk, scandisk, almost EVERYTHING!). The problem was the partitions, the USB stick installation has made 3 partitions: a small NTFS, a FAT32 EFI, and the large NTFS. I think Parallels could not handle that. Removing partitions just caused boot errors. Here is the solution: 1) add a new virtual machine using the Windows 8 Preview Release edition buttons provided (get the 64bit edition). 2) when that machine boots, go the the microsoft site that offers the 30 EUR upgrade option. 3) After paying, do not select "download ISO" or "download to USB stick". Take the install now option! 4) if you upgrade your preview edition to the RTM in that way, you only get 2 partitions. Everything works well then, compressing the HDD is no problem. it took me a lot of hours to figure that out. While the Parallels manufacturer just says: a new Windows 8 installation should work just fine yes sure, but you have to know how to do it.....
