There are a number of issues and pointers here. Firstly, in order to flash your BIOS, you would not need any hard drive - you simply need to download the flash onto a floppy disc which you then use to boot up your PC. HOWEVER, back to basics. DO you really need to flash you BIOS. This is not something you should do unless you know what you're doing. A mistake here could prove very costly.
However, if you really do want to go ahead, and all else fails, use a partition manager to create an E:\ drive, run you rflash, then you can dlete the partition again.