I am connected to a wireless network some 500 meters distant using a wireless pci adapter with an external antenna. My system is windows xp professional 'new' edition. I originally set this up using a qpcom wireless pci adapter 802.11g. Due to the weak signal that I received, I changed the wireless pci adapter to a D-Link 802.11b which improved the signal tremendously. Of course I had to use the same ip information. Now I am receiving messages that I have a possible ip conflict. How do I correct this situation?

Log into the router and check the IP range/lease settings in DHCP.
Are you running on static or dynamic IP's.
Makes things easier if it dynamic then the routers DHCP will allocate IP's as needed.

Ps 500 Meters is right on the edge for successful wifi connections. Is it possible to resite the access point ?

My internet connection is supplied with this connection. The ip address is NOT automatic. The connection is great, I simply wish to remove this warning from my xp installation.

Well in that case just change your IP to something completely different.
To ensure it well aout of the way add 100 to the end number, e.g. if its 192.168.0.25 make it 192.168.0.125

I cannot change this ip address. It is supplied by the network administrator. If I change the ip address I will lose the supplied internet service. I have no control over this network other than my wireless lan adapter.

OK, so talk to the Network admin and get them to fix the problem.