Even USB 1.0 should be more than enough for all but the fastest of DSL speeds. IIRC, USB 1.0 was around 1Mbps, and the fastest DSL speeds you can typically get is 1.5Mbps. USB 1.1, which is much more common, is 11Mbps.
USB 2.0 requires all new hardware to support it. It's not as simple as a software update. You can buy PCI cards which will add some USB 2.0 ports to your system, or you can buy a new motherboard with USB 2.0 support.
But I suspect your problem has more to do with spyware. Download and run BOTH AdAware and Spybot and delete everything they find. Then see if that doesn't improve your speed a bit.
Otherwise, more details are going to be needed. What speed DSL do you have, and what speeds are you expecting? That's for starters, and depending on your answers, more maay follow.
My machine is running XP with 480 mg ram and 1.66 ghz. My DSL is running really ssssllllooooww. I had the telephone company come out and check the lines and on their lap tops it runs fine. So that rules out my modem and lines. The only thing I can figure is that since I am using a USB 1.0 that this may be the problem. How hard is it to change the USB to 2.0 and can you direct me to where I can get what I need to do so. I have a little experience with changing components. Cannot use ethernet because my card is bad. Maybe it will be easier to cure this problem?
Machine is HP 541 c if this info is needed.