They do, and they all look fine.

Next step would be to at the relative CPU usage in Task Manager of processes and see if something unexpected is using a lot of CPU time when doing both speedtests and normal downloads

I have seen very similar problems testing on my Dell Vostro 1700 laptop (Core 2 Duo, 2.2Ghz, Windows 7 Professional 32 bit), just tested (remotely using Logmein so results will be a little skewed) and CPU hits 100% during the HTTPx6 test - that appears to be what's limiting my throughput on this particular test.
Normally use Pale Moon browser, TBB x1 download gives about 53Mbps (doesn't quite max the processor), HTTP x6 gives a result in the twenties (last test Avg 24Mbps, burst 28Mbps), tried with IE9, this improved the HTTP x6 test to about 34Mbps Avg and 36Mbps burst while maxing out both cores on my CPU.
Disabling (Avast free) antivirus and (Windows) firewall makes little noticable difference.
When I look at running processes, the browser is the thing using greatest amount of the CPU (though nothing like the 100% reported in total usage), Flash player shows too but with quite low % displayed.
@MrSaffron, all was fine until I ran these speedtests, I recon you owe me a new (faster) laptop

[edit], I have Vista on the same machine, I'll need to try that for comparison (can't reboot into a different OS remotely though so that'll have to wait until later).

Edited by deleted (Wed 20-Mar-13 12:39:47)