Everything looks good. If you to improve on your components, the price will go up and I don't think you want that. That power supply looks good, but may be overkill for what you have. It's still good to have though if you're willing to pay for it. The video card looks pretty ancient. I would get at least a Geforce FX video card. The RAM is at the minimum so it should be ok. Get a DVD burner instead instead of just a ROM. The hard drive will work fine and even if you get a newer SATA drive, you probably won't notice too much of a difference anyways.
Is that a PCI-e supported motherboard? If not, than you can get this for the video card:
CHAINTECH SA5200-256 Geforce FX5200 256MB DDR AGP 4X/8X Video Card - Retail
For DVD RW drive, get this one:
LG Beige 16X DVD+R 8X DVD+RW 8X DVD+R DL 16X DVD-R 6X DVD-RW 5X DVD-RAM 16X DVD-ROM 48X CD-R 32X CD-RW 48X CD-ROM 2M Cache IDE DVD Burner - OEM
NOte that you may need to purchase additional software for burning if it doesn't come with one or just use Media Player.