DLink Router Problems

[Noskill]

Hi there! I'm having a problem with my Counter-Strike Source server that I'm running at home on my computer. Whenever I start up the server, it always ends up with a different port number, like:

externalip:50000-60000, seems to be within that range of numbers

No one can connect to my server because of this problem, I was wondering if there's a way to stop my router from changing the port number all the time.

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Server OS: Windows XP Professional, 32-bit
Processor: Intel Pentium 4 CPU 3.06GHz (2 CPUs)
Ram: 2 GB of RAM
Game(s): Counter-Strike: Source
Start Up Command: "C:\Program Files\Valve\HLServer\srcds.exe" -console -game "cstrike" +map cs_italy +maxplayers 6 -port 27015
Admin Mods: SourceMod, Metamod

NETWORK AND BANDWIDTH INFO

Bandwidth:
DLink DI-524 router, REVC, wired
Local IP of Server: 192.168.0.102
External IP: 99.234.243.113
Port forwarding screenies below
[Server] --> [Router] --> [Modem] --> [Internet]

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