You can only download as fast as your ISP is providing you, (what your plan is)
You can try this, TCP Optimizer (XP)
This will optimize tcp settings - personally this is the only thing that actually helped me and I have tried many - Not going to get you to blazing speeds or anything, just optimizes settings to work with what you have - Remember, can only work with what your ISP is providing under your plan.
No promises, but will help if noticeable. SpeedGuide.net :: TCP Optimizer / Downloads
What you can also do is go to Speedtest.net - The Global Broadband Speed Test
And check your up/download speeds before and after