factors influencing a users download speed. With shared bandwidth the speed fluctuates depending on the number of subscribers on the network. With DSL, the connection is yours and not shared, and you tend to have a more constant speed. This is one reason why cable Internet providers don't often publish speed information. In more rural areas with fewer subscribers, you're bound to have faster download speeds than a subscriber in a metropolitan center. Because cable modem speeds fluctuate, it is difficult to gauge an exact download speed. On the upload stream, however, cable and DSL are closely matched for speed. Both DSL and cable Internet speeds are largely dependant on the service provider and either the distance away from the switching station you are or how many subscribers are in your immediate area.
look for TCP-IP optimizer check for version 1
http://www.speedguide.net/
& have u made a ping to testmy.net to check if you have packet loss?
just type "cmd" in run, at the prompt type ping testmy.net,
results?
have a look at this site as well it will answer your questions in detail and give you some hints..
http://www.dslreports.com/speed
then if you still have probs
call your ISP to check your signals.