Hello. I am upgrading my system and I have a old system, by that I mean I have an AGP slot and not a PCI slot of videocard. So I tried to find suitable videocards for me and decided to buy a Geforce 6600 GT. --I want to know that is there any major difference between 256mb and 128mb version of the card because I could not find a 256mb version of the agp. --Can I run the AGP 8x card on AGP 4x? --How long is this card going to work fine, I mean for how long I dont need an upgrade after buying this card? Thanks.