Giving a new life to an old SPARC machine - boot and install related problems

My problem isn't one you encounter on a daily basis, yet I find interesting enough to share and ask for help. From the beginning: the academic scientific group I am a member of (we are focused on networking-related stuff) got today an ooold SPARC server, which we intend to use as our www/shell account machine (currently we use a pretty poor virtualized solution).

Here's a photo of it: http://i.imgur.com/s8iE9.jpg

The big question is: how do I find out if it's functional and install an OS on it? The thing hasn't got a VGA port which would make things way easier.

We've got a cable that looks like a DB-25 -> COM cable, but it's been reported not to work on a windows laptop with hyper terminal. I've been thinking about monitoring the network ports for any kind of traffic to confirm it's functional and then fiddling with network boot to install any OS on it - is it any good of an idea?

Thanks in advance for any help :)

Time for update #1:

I'd like to thank everyone for their advice! It was all very helpful, however I've run into some problems today. The first problem: http://i.imgur.com/tFgv5.jpg

As you can see, the thing on top was not a Sun Netra, but a StorEdge S1 disk array. The other thing is that I don't have a key, and the manual @lain says that you have to turn it on in the diagnostic mode to get a serial console. My google skills seem to be bad, @voretaq7, because I can't seem to find any information regarding turning on the diagnostic mode :-( Could a locksmith make a key that would fit provided I found a blueprint of the original key?

Here is the other photo: http://i.imgur.com/eFsEf.jpg

That's a big amount of ports there :-o How should I attach the StorEdge to the 4500? I browsed through it's manual and it seems like plugging one end of the SCSI cable to SE's out port and the other to the ,,1'' marked port on the 4500 is a good idea.

As for the DB25->COM cable - it turns out it was custom made, and probably isn't a null-modem one. Where could I find a diagram so I can make one?

Final update:

I'd like to thank everyone for their input :) You helped me a lot to get the machine running and I don't think I would be able to do it without you. http://i.imgur.com/A9obl.jpg - currently running OpenBSD, but I'll tree Free later on :) Cheers!

First off, what models are they -- The little one on top looks like a Netra of some kind. The big one is obviously an Ultra Enterprise 4500.

Second, quick crash course on Sun hardware, probably applicable to the box on the bottom more than the one on the top:

• As others have pointed out, if you want to use video you need a 13W3-to-VGA adapter (or a Sun/13W3 monitor).
  You also need a Sun keyboard - If you don't connect a keyboard…
• …You can use a serial console (or HyperTerminal on a Windows machine).
  • Connect a null-modem cable between serial port A on the Sun machine & your Windows box or serial console)
  • Open up HyperTerminal & set it for 9600 baud, 8-bit bytes, No parity, 1 stop bit (9600/8/N/1).
  • Turn on the Sun machine. You should get dumped into the Sun boot monitor (and if an OS is installed, eventually a login: prompt.

From there an OpenBoot command reference should get you where you need to go in terms of getting the OS up and running or installing a new one.
If you don't want to run Solaris I would encourage you to consider NetBSD or OpenBSD - I'd lean toward the former if you expect to get a lot of heterogeneous "inherited" hardware, as you can install NetBSD on pretty much anything.

Beware of sending the break character once the OS is started (this often happens when a serial console is turned on, or when some USB-to-Serial adapters are plugged in). This will cause the machine to drop back into the boot monitor (suspending the OS and leaving you at an OK prompt) -- Should this happen to you inadvertently, just type go and the system will return to normal operation.

Assuming the box on top is a Netra it's a bit different -- There's usually a combination serial and Lights-Out-Management (LOM) port that you connect to with a Cisco-style console cable (9-pin to RJ45). This Page has instructions on fabricating one, but you can probably buy the cable for a small pittance and save yourself the work.
This page talks a bit about how the LOM system works (basically type #. (hash period) to get into it and it's a stripped-down equivalent to the boot monitor with some other capabilities).

Of the two the bigger box is likely to be better/more useful, assuming it wasn't stripped of all components of value.

Note: Some Sun hardware only has one serial port, marked "A/B" (I think the 4500 may be one of these but SunHelp disagrees) - on the off chance it is, I believe a regular serial cable will hit port "A" which is what you want. SunHelp's serial ports and pinouts page is also a great resource, as is the rest of the SunHelp site.