How do you undo Extrude? and the selection looks like half a circle. i've tried selecting the part and going negative in the extrude, but that leaves the edges there.

i know about that, it's just that i didn't need to do the undo until i was finished with some other stuff so i can't do that, and i haven't saved yet.

Ok Thanx ColdFire, I'll find another way to do what I was going to do.

lol nice avi and quote.

Well, if you did so many steps after it that the undo button runs out, then It'l be hard to undo. You can delet the entire thing you extruded, convert it to an editable poly, go to create, and create a face around the gap by clicking on the verteces on the edge of the gap sucsessivly. It will create a face to fill in the hole. Then in the modefiers list go to StL check and put a check in the "Check box". Make sure the entire map is selected when you do this. If there are no errors and everything looks good then you did it, otherwize, you're now even more skrewed up, sorry.

o wow u screwd him up

open autoback 1,2 or 3 ( cant remember defaults i think its just 3)

lol i no i had to redo my bases once. kinda hard. if i wer u i would save as i go. kinda like checkpoints. very useful

just click the undo button, or do as maniac mentioned and go to the autodesk folder in the program files folder.
look for the autoback (autobackups folder).
select a save which has not got the changes added.
or even just delete the polygons where you extruded, then seal the gap.

get used to adding backups of your work with my_map edit1, edit2 etc.
autoback up saves roughly every 5 mins and will save 3 times then overwrite the old backup.

you can go into the customize and change how many autoback ups are saved for you while you work, pretty sure you can also change the set time to auto save aswell.

This is one of the biggest bumps I've seen, thats 4 years worth of burying undone. :P