Yes, connect the external HD to a usb port? You can either buy an
external hard drive, a unit that already has the hard drive built into it, or you can make an external drive by buying an external enclosure and then installing any IDE or SATA hard drive in it; just be sure to buy an enclosure that's designed for the type of hard drive you would be installing in it.
You can copy the files over simply by opening a Windows Explorer window and executing the copy from there. If you want to backup, rather than copy, you can use the Windows Backup utility found under Accessories, System Tools.
If you copy only your photos to the external drive and no executable files, you will not re-infect you computer. Still, once you get your files copied to the external drive and get your system back up and running (virus -free), then I would scan the external hard drive with your anti-virus software.