Really shocking problem with download

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Hello,

I have a strange problem since I format and reinstall windows XP SP2 last week

I have always 3 or 4 IE window running at the same time. I surf and work on many forum at the same time.

My problem now: If I download a file and all my windows of IE are openned, my download speed is really slow..........20-25 kbs. But If I minimize my windows, my download speed increase to 400-500 kbs Same if I try to load a page and I don't minimize my other pages, it will load relly slowly.

I really don't understant why I can't have 4 or 5 IE windows loading at the same times like before my format

Sometimes my modem is restarting too when I open another window......This is a really new and strange problem.

I need your help again my friends

P.S. I have two monitors in my video card and since one year I had no problem.