Why do I have more than one rundll32.exe listed in my task manager?

There is a suggest that some viruses run as rundii32.exe
(you can check this if you are running XP Pro by typing TASKLIST in a commandline to find out whats running on your system.)

Other possibilities include that a homegrown Visual Basic Application could be using an instance of RunDLL32.exe to access the device library, such applications could be the Script Kiddie Zombie processes that are for instance Port scanners that don't close down properly and sit in the background of your system waiting for an IRC Server to house a particular Channel etc.

A less horrific occurance of such an application could just be the drivers to a Peripheral that isn't 100% compatible with your version of OS and therefore it's using older methods of accessing your system to run correctly.

I'm afraid without a bit more information through diagnostics theres not much more I can put down.

And, uh, how do I check these things? Sitting with XP Home.
What do you mean - not 100% compatible? Everything I have so far said that it is compatible with xp home edition.

try downloading Process Explorer by http://www.sysinternals.com/
it should give you some extra information.

It is probably a virus using the same name.

It says it's not a valid Win32 app. :bugeye: