Setup:

Athlon 3000+ Barton (333 FSB) no oc.
512 DDR3200
80Gb Maxtor IDE
DVD+CDRW
ASUS AV7X-X
GeForce FX5200 256Mb
Win XPpro

USE:
Little bit of gaming but tends to be stuff a year or two old
Digital image editing
Basic other uses

Q: Is it worth upgrading the memory to 1Gb?

I've thought about it for a while but I'm really not sure if I would notice any difference.
Machine does tend to bog down a bit if I'm using photoshop with other things (especially after SP2) and I wondered if the extra 512 would smooth it out a bit.