Can I improve graphics performance of my iMac?

iPlayer is great and I have a fast connection but audio runs ahead of video; I assume this is because the graphics processor is not fast enough. My iMac is fairly old, the hemispherical plant pot model, and I realise doing anything inside will be difficult, unlike my even older Mac G4 where, without any tools, one can unhinge the whole side of the case. Data on my iMac:

1 GHz PowerPC G4
512 MB DDR SDRAM
10.4.11

NVIDIA GeForce4 MX:

Chipset Model: GeForce4 MX
Type: Display
Bus: AGP
VRAM (Total): 64 MB
Vendor: nVIDIA (0x10de)
Device ID: 0x0189
Revision ID: 0x00a3
ROM Revision: 2032.2

The best thing you can do is upgrade the memory. You can get 2GB RAM or perhaps 4GB pretty cheap. Try http://www.crucial.com/uk/. This is where I've got my Mac memory in the past.

Your iMac officially supports 1GB of RAM, unofficially 2GB. Adding more will increase the capability of the machine - Tiger will be dog slow with 512MB ..... but as you guessed the now aged 32MB graphics really cannot cope with processing todays streaming video - so thats your bottleneck. No upgrade possible for that I'm afraid.

It's not too difficult to fit a 1GB stick:

http://www.info.apple.com/usen/cip/pdf/imac/imacfp.1...

Great looking machines imho, I have one laid up here somewhere......

MrMemory are another option and have served us well in the past.

Matt