I had a similar experience with my pc.... ie - stuck with an old version of IE using an old version of Windows XP. My machine was purchased in 2001, making it 10 years old now. So earlier this year, I re-built it and installed a new version of XP (Black Edition) I was then able to upgrade to IE8/9. It now runs very speedily indeed and is well-up for what I use it for. I will be buying a new PC in the new year, probably based around an i7 processor.... but for now, my PC is fine and by re-building it (ie reformatting the HD) I've managed to get another year out of the old dog!

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