Well, as far as G5's go, Apple never modified "them with intels". They replaced the powerpc machines with new machines using Intel processors. The power PC machines were known as power Macs, and the intels as the Mac Pro series.
There were actually 5 iterations of the G5 powermac - http://support.apple.com/specs/#powermac
You can use the "about this mac" from the finder to see which one you have once you get it. Or, pop the side door off and look at the bottom of the frame for the model number, and look it up on the linked page (above).
At my old job, I had a dual quad-core liqued cooled G5 for awhile - I really liked that beast.
OK, as noted above, though the case looks alike, the Mac Pro and Power Mac G5 machines are quite different. The configuration label will have, among other things, the serial number of the machine. It will also have the "as-shipped" configuration, though that may have changed as drives are replaced and memory is added and maybe a video card is changed. The configuration label is located on the inner frame of a G5 in the center of the lower frame below the plastic air deflector and probably in the same area on a Mac Pro, though I am not positive about that.
You can use that serial number at the Chipmunk site to get more information. EveryMac has a specs lookup site which is based on the identifier of the machine, which might look like PowerMac7,2 or other numbers or maybe MacPro5,1 or other numbers. Once you get the machine up and running, you can select the "About this Mac" item from the Apple Menu and then click the "More Info" button, which should brink up System Profiler, which offwer a wealth of information about the system.
Finally, you can obtain PDF versions of manuals for the machine in the Apple Support area, in case you don't get them with the machine.
Ok, I had a look at them today.
I didn't realise there were two G5's hehe!
So, they are G5's PowerMac's.
What limit can I upgrade them to with no discs or anything.
They both have a single HDD SATA in them, and a spare slot.
Can I just purchase any old SATA HDD or does it have to be something special?
What RAM can I upgrade them to?
Assuming they are just 1gb with 80gb in there.
I wasn't allowed to remove them from the office due to them being negotiated with 'cleaning' by the liquidators.
I noticed that the machines both have two DVI outputs on the back as well, I don't know if this helps.
Any one with help would be much appreciated.
The SATA drives must be SATA 1.5 Gb/s compatible, & up to 2.2 TB in size requires nothing special.
You'll need Retail OS Discs to install any OS on them.
Tiger or Leopard.
To use Mac OS X 10.4 Tiger, your Macintosh needs:
* A PowerPC G3, G4, or G5 processor
* Built-in FireWire
* At least 256 MB of RAM (I recommend 1GB minimum)
* DVD drive (DVD-ROM), Combo (CD-RW/DVD-ROM) or SuperDrive (DVD-R) for installation
* At least 3 GB of free disk space; 4 GB if you install the XCode 2 Developer Tools (I recommend 20GB minimum)
See Tom's, (Texas Mac Man), great info on where/how to find/get Tiger...
Or Ali Brown's great info on where/how to find/get Tiger...
* Mac computer with an Intel, PowerPC G5, or PowerPC G4 (867MHz or faster) processor
minimum system requirements
* 512MB of memory (I say 1.5GB for PPC at least, 2-3GB minimum for IntelMacs)
* DVD drive for installation
* 9GB of available disk space (I say 30GB at least)
Trouble is Apple no longer sells it, check eBay & such for the Retail version, not the Gray Discs...
If you don't know the model, find the Serial# & use it on one of these sites, but don't post the Serial# here...
How to find the serial number of your Apple hardware product...