title says all.
It shows me having 24 comps, but in reality only have 9...

You have to do it at each project.

You can only delete a computer if all the result information for the computer has been removed from the database.

If you have duplicates, you can try merging them. No guarantee it will work though. I'm sure someone will be along to give the criteria for merging above and beyond same hardware and same OS.

I went through and merged/deleted as much as the sites would allow me to do. The only one that I could not do it on was world community grid, as it timed out after 30 days. But there are still duplicates listed on many sites...

Well,

WCG is a beat unto itself. It doesn't use the standard BOINC backend. So you're stuck with those hosts.

Xtremelab is another, although it does use the BOINC backend, it wants all that host data (or something like that).

And climate prediction. There units hang around forever so you can't get rid of any machines there.

well at least it got me down to 20... now just to cut that in half...

Hey! I have reinstalled boinc on a pc, and now i see two times tghe pc in the stats... how i can merge?

Go to your account, list of computers, click one of the ID numbers of the computer with the double listing, scroll all the way down, merge computer, check the one you want to merge with, OK.