Could I have a virus on my external hard drive?

About a week ago I contracted a virus, and after scanning my system a couple times, AVG told me it was vundo.ka though it did not remove it completely. After quite a few more tries to get rid of it with different programs, someone linked me to your Malware Removal Guide, which worked like a charm, so thank you for that!

My concern is this: my external hard drive was connected to my system a couple times while my computer was infected. The most recent was today, when I was scanning both my computer and the external drive with SuperAntiSpyware (before finding your guide). It didn't find anything on the drive, but then it never found anything on my computer, either.

Should I be concerned the external drive is infected as well? Can it reinfect my computer? And if I run your removal guide again with the drive connected, would that work?

Thanks so much.