1) First step, we should verify that the server was successfully able to get port 25565. Type this at a command prompt:
[tt]netstat -an | find "25565"[/tt]
If you get a result that says something like either of the following two lines:
[tt]TCP 0.0.0.0:25565 0.0.0.0:0 LISTENING[/tt]
[tt]TCP 192.168.0.2:25565 0.0.0.0:0 LISTENING[/tt]
Then the Tekkit/MineCraft side of things is all OK. I suspect that based on what you have put in your server.properties file, that you will get the second line.
2) Now we need to check your PC's firewall.
In the bottom right corner of the screen next to the time, there should be an icon of a screen with a plug over it - which when hovered over says "Network xx, Internet access". Click this once, and select "Network and Sharing Center".
In the bottom left of the screen, it should say "Windows Firewall". Select this.
Click "Advanced Settings".
Click "Inbound Rules".
Click "New Rule".
Select "Port", click Next.
Make sure "TCP" is selected, and in the "Specific local ports" box, enter "25565". Click Next.
Make sure "Allow" is selected, and click Next.
Make sure all boxes are ticked, and click Next.
Name the rule something like "Tekkit Server" and click Finish.
Then give it another try.