Slow broadband connection

Hi There,

I've recently got connected to Plusnet's 2MB unmetered service and I can't
seem to get a decent connection speed. I have 2 PCs, 1 is a desktop running
Win Me, connected to a D-Link DSL-G604T wireless ADSL router via a DWL-G122
USB (1.1) adapter. The other is an IBM thinkpad T41p using a wireless lan
mini PCI adapter, Win XP, which also connects to the router.

With the laptop I can get very close to 2Mbps, but with my desktop, the best
I can get is 433kbps, although it averages 400kbps

I have the following security options enabled WPA & Mac address access
control, don't know if this affects anything, although doesn't seem to affect
the laptop.

I tried installing a 2.0 USB card and wired network interface card, the
results are below:

Using the USB 2.0 card: No difference. I even moved the AP right next to the
USB adapter so that the signal strength was 100%. No cigar.

Using the NIC: Connection speed lept up to around 600Kbps which is an
improvement of approx 50% but still no-where near the consistent 1.8Mbps I
can get with the laptop.

Do I ditch ME and trying upgrading to XP? Anyone got any other ideas on
other settings I could change on ME box?

Frustrated.
Pep