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To be honest I can't remember what did get the C, I changed all the letters I could as soon as I realised. On my computer I have one hdd, one dvd drive, and two memory card slots. But rather than one of them getting it I think it's more likely that when it was being fixed they put another drive in and then took it out later. As far as I know the first harddrive is always given C.
I don't mean to sound like I'm questioning you here, but I find it extremely odd that my OS would just be fixed to loading from F permenantly unless I formatted the drive, especially since F is 3 letters away from C. The program I'm using lets me set it up, and puts the change in the 'operations pending' box. Admittedly I didn't click apply, but that was because I don't want to end up with a system that wont boot.
Theoretically, if I could forceably change the letter of the boot drive, would the booting program recognise that it had changed and load it off the new letter instead? I don't really know enough about it, except that BOOT.INI is something to do with it, and it doesn't actually say F in there, just multi(0)disk(0)rdisk(0)partition(1).