On power-up F2 gets you into the BIOS setup screen. The BIOS is a standard AMI BIOS. My Optiplex 160 was running BIOS A01. Going to the Dell website I found the latest BIOS release for the Optiplex FX160 was A13 dated 17 July 2013. Having downloaded this and run it I got the message "The system can NOT be updated with the BIOS file, click Cancel to exit."
[Back in November 2016 I wrote: "Why not?". I now know the answer to that is that I was trying to install the Optiplex FX160 BIOS on the Optiplex 160.....]
At that time, remembering my past experiences with Dell kit I went to: Dell support -> autodetect -> install "Dell System Detect".
When I ran this software it took me to BIOS 160-A10 dated 10 July 2012. This installed without any problems.
As you would expect, I subsequently found that that BIOS will not install on the FX160 but the Optiplex FX160 A13 BIOS will.
On power up the F12 key brings up a boot menu. As far as I can see the BIOS just lists all the possible boot devices it has found on the system so that you can pick what you want. That's the manual way of booting something.
Originally I didn't spot the BIOS entry for setting the boot order and thought there was no way of doing this. However in June 2023 Matej put me right. The usual place for the boot order is in one of the later BIOS screens but the FX170 BIOS differs here in that it is on the main 'System' screen that is shown on entry to the BIOS. However the option is off the bottom after the 'Processor Info' and 'Memory Info' and you have to scroll down to find it. (ie It is not immediately visible - I should have spotted that there is a scroll bar on the right-hand side of the window).
The 'Boot Sequence' offers five boot devices that will be tried in turn and each entry can be set to:
The final screen in the BIOS is labelled ImageServer. It's introductory text reads "These fields are active when the integrated NIC is set to ON w/ImageServer ". I haven't researched this but it would appear to be some kind of Dell variant on PXE booting. Checking the Integrated NIC entry in the 'Onboard Devices' tab I see the options there are Off, On, On w/PXE, On w/ImageServer.