[question, lua, computer] stopping the pc from opening a disk on startup

I'm trying to make a firewall for a virus I made and I need to know if its possible to stop the pc from scanning disk drives first

Yes, but the only way is to modify the shell (in rom/programs/shell), so you can't do it in a server you don't have access.

so you can't edit that folder from ingame even using fs.delete/open?

No, that's why it's called rom: Read Only Memory.
If it's on ssp or you have access to the server files, you can go to ".minecraft/mods/ComputerCraft/lua/rom/" and edit the files, otherwise there's no way to do it.

ok but what about a program that detects if there is a disk and eject it if there is…and sorry for being such a noob :P/>/>

That's possible, but it won't prevent the startup on the disk from being run. The startup from disks is run before anything else (of course, after the bios and shell).