Re: Memory - 1 GB
2 x 512MB is quite a lot better if you use them in dual-channel config, while you'll probably get a slight boost if not, because of reduced latencies (unless you get an expensive low-latency 1GB stick)
64-bit computing and Windows Vista means more RAM is needed, so you might wanna go with 1GB stick, but if you won't be taking those routes within a year or two, then you might wanna go 2 x 512MB.
Windows XP Pro 17" LCD Monitor (1280 x 1024)
nForce3 250 Chipset Athlon 64 2800+ w/ C'n'Q
1 x 512MB DDR400 CL3 SDRAM 40GB IDE 7,200rpm HDD (8MB Cache)
nVidia GeForce MX420 64MB PCI On-Board Audio