|There's no such Optiplex model.|
It's either GX280 or SX280
Go here to find your Service tag number, tell us what it is:
"cannot boot on dell- system password keyboard wont work"
Are those 3 separate problems ?
What do you mean by cannot boot ?
Is there no response at all from the computer ?
Do you see normal video while booting but the operating system won't load normally ?
If you DO get video while booting, if the keyboard won't work, use a different keyboard.
The password for what ?
For a Windows user,
or for the computer itself (a password set in the bios Setup - a system access password you must supply it to use the computer at all),
or a hard drive access password (you must supply it to use the hard drive).?
If it's a system access password, when the AC power has been disconnected to it, remove the Cmos battery from the mboard for a short time , install it again with the + on it showing when it's installed. Boot the computer - you will get a "Cmos Checksum Error" or similar message - go into the bios Setup and set the date and time, Save bios settings to get rid of that message while booting.