You may have to hit another key, instead of the delete key.
Attempt F11 or any of the F keys during the boot sequence. Watch the screen carefully for instructions, in case it does show what key to press while the BIOS is booting up.
It might take a while, since there are a lot of F keys....
If you aren't using a PS/2 or USB keyboard, it won't work either. Bluetooth keyboards require the bluetooth drivers to load before it can be used (Windows).