I had to reinstall Windows on my PC after the Service Pack 3 installation went wrong due to an incompatibility between a new RAM module and my motherboard. After installing Windows and all drivers, I attempted to connect the PC to the Internet via WLAN. Under Windows XP, when I refresh the list of available wireless networks, my router is listed and Windows also tells me that the connection is secured. However, as soon as I tell it to connect, an error appears after five seconds informing me that the network suddenly disappeared or that there is another unknown problem. After that, the network is listed in the available networks again. If I try to manually add the network to the list of preferred networs and type in the WLAN key, Windows throws out an error shortly after confirming everything that connecting to my network failed. I also installed Windows Vista on a second partition and the situation there is worse: the network isn't even listed as being available. I also tried rebooting the router without success. The only thing that I didn't try yet is to reset the router configuration, but it would be a pain to reconfigure everything.

Any idea what might be wrong?

PS: Don't come with ideas like "don't use WLAN" since otherwise, I would have to use a cable that is at least 15 m long (+ it would look ugly ).

It worked before SP3? SP3 is still in beta, it's quite possible that that could be the cause of the problem. Hell, even finished service packs often cause problems like this.

When service pack 2 was released I remember that installing SP2 on an existing XP installation caused compatibility problems with certain applications whereas if you slipstream SP2 on the CD and install XP SP2 fresh, it wouldn't cause the same problems.

TBH I always slipstream, I dislike installing something as critical like a SP

Oh: Bah @ WLAN

I forgot to mention that I currently have XP Service Pack 2 installed (and yes, I installed from a XP SP 2 CD). WLAN used to work before reformatting...

I managed to solve the problem. The AVM FRITZ!WLAN USB Stick drivers were installed correctly, but the stick only seems to work together with its own software for connecting. I also installed that and everything works fine now.