Yes I know that but I need the "install" directory to upgrade ..If i have it in the root dir I can't access the admin panel unless i remove it..
I can't help but think you have a few steps backwards here:
1. First you upload new vBulletin files to the server.
2. Then you navigate to the upgrade script and run it.
3. Then you delete your install folder.
You have no need to access the Admin CP until AFTER you've finished with the upgrade.
If you did these things out of order, then that's part of your problem. Reupload your files again, and make sure to not delete anything until after you've finished with the upgrade script. It will tell you when to do that.