I'm not too sure what you mean. I have a MyBook 320 GB 2.0 via 2.0 USB. I connect it to vista, and I hear a little ding sound, but it's not showing up anywhere.
Your external HDD has to be formatted in FAT32 or NTFS for Windows to recognize it. If it is formatted in the Mac's HFS+ file system, Windows can't do anything with it.
Boot Camp should, for all intents and purposes, be no different then a Wintel PC, at least as it relates to hardware. The only real differences is Boot Camp provides a virtual BIOS for Windows, but hardware like a camera or microscope should not care about that.
took the words out of my mouth. it must be ntfs or fat32 to have windows see it. if you have it in hfs+, which is the default for osx, then windows will not see it