Strange windows start up problem !

Hello there

I am having a strange problem with my PC with WINDOWS XP os

The thing is that i have an Hi-speed Internet router, when i start up my pc
it boot up fine no problem, until the windows xp logo screen the bar run like 4-5 time no problem,
then it open up to Windows deskop screen, Now is the problem the deskop
will freez like 2-3 minute before i can do any thing and while this happens it will only show the background of the deskop,
after a few minutes then it work fine again the icon and everything appear and works good

But now this is the strange thing, When i start up my pc and switch on the router so it gets conected to
the pc, It work fine no problem at all, the boot up start up to deskop screen no freez at all take like 45 sec to
get the pc ready to use

but ! when the lan and router is disconected then i get the same problem when the deskop first appear

i tried to take the lan cable out but it's the same so now the only thing i can do to let my pc start up in 45 sec not 3 minute is
switch on my router !

What is this??

I have Xp pro pack 3, my pc spec Intelcore2duo 2.2 Ghz 2Gb RAM VGA GF9600gt

any one have any clue , THANKS