I have cable and my downloads slow down when doing more than one. Your pc tries to balance the downloads.

 

Becareful overclocking that processor. It tends to run on the hot side anyways. Every time i burn a dvd i have to point a desktop fan on my case to assist in cooling process. I am running about the same setup speed wise,but i prefer different brands. Check to see if your motherboard supports a core 2 duo proccessor. If it does then you might think of upgrading. They are supposed to be about 40% more efficent than the pentuim Ds. Plus run cooler. I have 2 120mm fans, 1 80mm fan, plus a 120mm in my power supply w/ all round cables to increase air flow and my computer still seems to run hot. I have never used the pc cillin program, but if you are looking for a low resource anti-virus go with avast or avg. Both are avalible at www.download.com. I had a lot of driver problems getting my pc up and running. I tried running linux with no luck. Ended up going with 64-bit xp since there were very few motherboard drivers for linux.

My pc:
Asus motherboard w/ nvidia chipsets
Pentuim D 830 3.0 Ghz
2Gb dual channel ram (side note: Check to see if your board supports dual channel ram.If so check to see if you bought duel channel ram this will improve performance)
2 nvidia geforce SLI 8600gt video cards (256mb each)
130gb SATA hard drive
dual dvd drives (1burner, 1 read)
64 bit operating system. (sucks not a lot of drivers)