The problem is the following:

I have a wireless Network (infrastructure mode) with a wireless router
as base station that is hooked to the internet.

Then I also have an onboard ethernet port which I connect via another
router to a network that hooks in with another computer.

Now how can I tell the computer that when accessing the internet it
should always use the wireless connection, because as soon as I enable
the ethernet connection internet doesnt work anymore eventhough the
network adapter still has everything assigned to it by the wireless

2 network adapters each receiving ip's from different dhcp servers
only 1 is hooked to Internet

just not working together... works fine though if only 1 is enabled at
a time. (very confusing) so why is it that on adapter has prevalence
over the other ? how can I change it.

I have Windows XP Pro SP1
Sitecom Wireless USB (+wireless router)
3Com 100Mbit ethernet (+ router)

thanks for replying