Port Forwarding for a change!!

[koolvankleef]

I could never seem to set up forwarding on my old crummy BT router and thought it was a firmware problem.
So I get a lovely new wireless Zylex 660 router and try again.
I've programed the SAT settings for ports 6699 and 6257 to forward to my computers IP.
I let WinMx do it's little testing routine and it can't make those connections.
Just to discount some stuff I've disabled my software firewall, that made no difference.
I used dial up and the computer could listen on those ports.
I've applied the XP service pack 2 patch
So it definately seems to be thr router or maybe my ISP (plusnet in the UK)
Does having a Dynamic IP make any difference.
i'd like to make me filesharing as efficent as possible.
Any advice gratefully accepted.

[koolvankleef]

Also I've just tried changing the ports that it listens on to see if it's my ISP.
how can I test if it' is listening on these ports. Ta