Windows 7: Slow Data Transfer Rate

I am planning on re-installing Windows 7 onto my computer to clean it up a bit. I have a 1.5tb external hard drive plugged into a usb hub, which is plugged into my computer. Whenever I try to copy files to my external hard drive, the transfer rate is extremely slow. When I start, it is about 10mb per second, then over time, it slows down more and more until finally it sits at about 40kb a second, which is extremely slow when copying gbs of data. USB 2.0 is supposed to transfer up to 600mb a second. I know it probably wouldn't be that fast but, I don't expect it to be in the kb range either. Any ideas about why this happens and what I could do to fix it?

USB is a shared BUS and shared CPU system. That means it will never reach its maximum speed more so if the CPU is under heavy usage. Also depends on how fast the External HDD can preform.

True enough, but under light CPU load (only background programs running) I could see 6-8 MB/s of transfer speed from to an external hard disk. This was on a laptop with an old Core2duo processor.

I use Teracopy to do the file transfers - it has a verify mode where it checks the source and destination to make sure the copy went through clean. It also claims to speed up copy by buffering both IO paths - I'm not sure how much that helps, but you may want to take a look at it.

attempt bypassing HUB, check perfmon for drive I/O statistics.

Yea, I'm using a core 2 duo processor, but I'm sure that the hard drive is rated over 40kb a second too, so I'm not sure why it slows down so much, I could deal with 6mb a second, but not 40kb.

This is a good suggestion, and might actually be your problem. Plug in the disk directly into the laptop, and check the speed.