I'm intending to update my graphics card. At the moment I have an Nvidia Riva TNT2 Model 64 which I think is starting to struggle with the newer games.Can anyone suggest a suitable replacement I am looking at spending around £150.
Any card you buy today will blast the old one to kingdom come, so your only real dangers are compatibility and overkill.
In general you are better to go for a card with Pro suffix (ATI) or Ultra suffix (NVidia), these have the best performance by far. ATI radeon seem to offer the best value for money at the moment.
If I had to pick one after just a few minutes searching, a good example would be Sapphire Radeon 9600 PRO 128MB DDR AGP TV-Out DVI-I, which is ? 96.20 incl vat from Ebuyer.com (search code 59146). This will do everything you are likely to want.
Check the following :
1) Make sure you have an AGP slot, graphics cards for PCI are harder to find and much much slower. 2) How fast is the AGP slot (i.e. 2X 4X or 8X) - if you don't have at least a 4X slot, you will not get very good performance. 8X is better. 3) If you pick a radeon card, remove your old NVidia drivers first.
If you go ? 12 beyond your budget, you could get a 9800 Pro, but to be honest I don't see the point.