1. Do you have Upload or Download bandwidth restricted in WinMX?
To check go to settings, bandwidth throttle.
Make sure the limits are both unchecked as they are here.
2. Have you ran adaware or spybot to make sure you are spyware free? If not I would suggest you click the links and download them.
3. What other programs do you have active?
Download Mike Lin's Startup Control Panel, disable all you can. See if problem is resolved. If so, add them back 1 at a time until problem re-occurs. then you have found the conflict. I also suggest Mike Lin's Startup Monitor for everyone, it is a valuable tool to avoid things entering your startup without you wanting it there
4. Are you using Zone Alarm Pro?
Some users use ZA P with no problems, others have issues of monstrous proportions running WinMX with it. If you are having a problem I would suggest a change of firewall . There are several good ones out there, I would suggest Sygate Firewall. (If you look at last item on page it is their free version, more than enough for average user).
5. Is XP firewall off?
This is a common issue among XP users, they are able to host a room , but no one can enter it. Even if you remember turning it off at some point in the distant past, check again. XP has been known to "remember" odd settings.
6. Are you protected against RTF exploits?
if not I would suggest that you download and install RICHED32.dll. We are long beyond the days of RTF exploits, but you can never be too careful.
Configured Router and still unable to host
There is a solution in the RCMS configuration file.
Open RCMSConf.txt (in your WinMX folder if you are running RCMS) and look for what is below:
[Loopback]YourAddress=Add your IP address here, not your routers address.
After adding your ip address to the location show, restart WinMX and try to host again. It is worthy to note that a domain name, or redirector such as no-ip.com can be used as a substitute for actual ip address. This can be valuable for users with a dynamic IP.