Hi. I'm trying to build a multiboot 16GB usb flash disk.. But always get som errors.. First I tried just to boot grub4dos from it, and make that loading a Windows 7 iso. That worked fine, until where I select what type of windows 7 I want to install.. It asks for a cd-rom device driver. Then I tried to boot a winpe image, and then start 7 setup from that, and then it worked for 32 bit, but not 64-bit. And after a little more searching i found this topic here And instead of trying this on my flash disk, I iused a 160GB usb disk. I partitioned it to 4 partitions, and installed norwegian xp pro sp3 and windows 7 32-bit (english, norwegian and litauian) on first partition, and 64 bit win 7 on second partition. It started just fine with grub, but I still get the "missing cd-rom device driver" when I try to install windows 7. I used "WinSetup-1-0-beta4" to partition, format, install grub, and install windows on my usb drive.