Hi, I have just been given a Mac Pro G5 2.8 GHz Quad-Core Intel Xeon with 4no 1 GB DDR2 FB-DIMM 800 MHz, is it worth spending money upgrading the ram & hdd's to use as a photo & video editing machine, if so how far should I go?
I have the same one you do (most likely): a 2008 3,1 Mac Pro. In my opinion, these machines are still usable (I still use mine), but they are not worth much or any new investment dollars at this time.
If you must upgrade it, put a little ram in it (don't go crazy, anything more than 4 GB should be fine) and a cheap SSD in it and try to leave it at that (a new graphics card would also be nice, though).
But, on the other hand, think about your budget and options for a newer Mac. Sell it for maybe $150 and put that plus your upgrade budget towards something like a low-end 2017 iMac, if you can stretch that far. That would be dramatically faster and better in just about every way than almost any upgraded 3,1.
(But if you do have a G5 vs. an Intel version, just donate or sell it for the value of its case, etc.)
I believe the 2008 3,1 dually 2.8's are definitely usable, plenty quick enough, and noticeably faster with an SSD boot volume. With these upgrades, I never felt the need to jump to the newer Mac Pro's as they were released. It was only when Apple officially discontinued OS compatibility with Sierra and newer that I finally made the plunge to a 2012 5,1. I did implement the OS patch to get Sierra working on it and it's been humming along nicely under Sierra (I've been using ASUEnabler to get OS updates, but the beta update option doesn't seem to work anymore).
Also you should list 1. What software will be used for Photo editing
2. What software will be used for video editing
3. Will 4K footage be part of the equation?
4. Will Color correction be part of the equation?
5. What video card is currently being used