:| why would norton do that? Are you sure it was the executable located in Windows\system32? rundll32.exe just executes a dll as if it were an executable. I'm sure you can require this quite easily. Though, I suggest you do so via the OS installation disk. If not, setup a VM, install the same OS as yours and rip the executable from it. (You can probably extract it via installation files aswell though.)
Most viruses take the name, so there is a good chance Norton deleted a executable with a similar name, in a different location.
There are two types of tragedies in life. One is not getting what you want, the other is getting it.
If you wake up at a different time in a different place, could you wake up as a different person?