I've used
Poser 7, with 1gb before, but I never did render with much in the scene, let alone 1/4 size renders. My little laptop is 1gb restricted, so I can't upgrade it further, so I use virtual memory with the 3gb switch for XP 32bit.
But for you...
I'm sure it's got the capacity to take more RAM, and if it's that old, it will be cheap too, I see no point in looking at other methods until you max it out the easy way first, which really is a memory upgrade. You'll find then things will work quicker also.
This may sound daunting at the moment, but honestly if I don't point you this way first I'd not be helping you at all. Especially as your PC needs it.
Google your PC model number, with the words (manual pdf). There you'll get the specs, for the maximum memory, and the slots where the memory goes for you to look up, and learn about.
If your PC is bespoke, then google (hwinfo), that will then get you a free program, which will tell you about your PC, and what hardware is attached. You'll want the motherboard information. Google that motherboard name with the words (manual pdf). That manual should give you information for what your memory options are, amongst other things.
With the PC model number or motherboard . Go to ebay type the model number followed by the word (memory), then look at the prices of the various hits that match. It should be cheap, you may see 1gb option, 2 gb option, or 4 gb option. That should give you an idea of cost.
You will want to look at the biggest memory option your pocket can handle.
Go to youtube type your PC or motherboard model number followed by the word (memory), you may see a take apart video, or an actual vid for upgrading memory. Learn that procedure, and with the manual you can carry out an upgrade yourself.
If there is no specific video for your machine, then watch a few memory upgrade videos, or take apart videos for similar looking PC's. That should give you a good general grounding on what you'll be doing.
Do it slow open the PC, with the manual as your reference see where the various parts live, and pay attention to the access to gain those parts. You don't have to upgrade straight away, build up your confidence looking at the parts first getting familiar with your machine.
Just remember not to go poking around, and do earth yourself to protect the parts inside the PC, as well as the memory that would go in.
What you're looking at is a 2-5min job, it's really quite straight forward, and will give you confidence with future upgrades.