- Windows 7 installation .iso file.
- No DVD, usb, floppy, zipdrive, etc, etc.
- A free primary partition already formatted as NTFS, let's say /dev/sda1
- Linux running at another partition.
- Grub (the one with menu.lst)
- Install Windows 7 into /dev/sda1.
- (Bonus) recover grub, still without external media [maybe I can just dd the first 512 bytes of /dev/sda and rewrite it once in Windows with "dd for Win"].
I've already seen some instructions but can't find it anymore after minutes of search. It was not that difficult, it basicly consisted on mounting the .iso and copying the installation files into the NTFS partition and make GRUB mount it. Then installation would follow (hopefully, although I guess the instructions supposed there were two partitions: one for installation files and another for Windows itself)