Photo resolution degraded in Internet Explorer

Hi,
I switched from ATT to Earthlink, and have two computers-a laptop with Win2000pro, and a desktop with XP. All is well on the XP desktop. When I look at items on ebay, or get an email with a photo, they look fine on the XP machine, but look very blocky and, I'm guessing, the resolution is down around 320x240 on the 2000pro machine. I don't know, but it is certainly worse than 480x640. Outside of the internet, the pictures I have stored from previous downloads look fine on this 2000pro computer. I typically upload at 768x1024, and the item on ebay looks fine if I'm on the XP machine, but really poor on the 2000pro computer. This is true not just when I look at something I have up for bid, but, everything I look at with the 2000pro computer, while on the internet, is poor, blocky, and of low resolution. As I said, outside of the internet, the resolution is fine on this 2000pro machine. It was fine when I was with ATT. I'm guessing the solution is somewhere in the internet options, but I can't find it. I am using IE 6.0 with service pack 4. My desktop is set to 768x1024 at 32bit depth. Can anyone help? Thanks.