Opening Ports For Steam

DragonMech

I am attempting to log on to steam, but I believe the required ports are somehow on use/blocked by another program. How do I open up the required ports? They are:

UDP 1200
UDP 27000 to 27015 inclusive
TCP 27030 to 27039 inclusive

My PC's specs:
2.53 GHz P4
512 MB RAM
64 MB DDR SDRAM

Internet connection speed: 100 MBps

Toshiba PCX1100U Cable modem

Using a Linksys 2.4 GHz 54g wireless router

Earthlink High-speed connection

DragonMech

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