go to the:
Control Panel\All Control Panel Items\Windows Firewall
and click on Advanced Settings in left sidebar.
Then search in Inbound or Outbound program you mentioned and check properties of software (game) you want to allow.
Be sure you checked in properties protocol and ports tab and both have correct settings for your game (since I don't how which ports/protocols HL uses.
Computer type PC/Desktop System Manufacturer/Model Number Self Built OS Windows 7 Home Premium x32 SP1 CPU x2 2.6 GHz Motherboard Asus Memory A-Data 2GB DDR2-800 Graphics Card ATI X1250 Sound Card SB 5.1 Live!
Keyboard BTC 6300 Mouse Logitech VX Nano PSU Tagan TG-480-U01 Hard Drives WD and Seagate FAP Antivirus None
System Manufacturer/Model Number Custom-built OS Windows 7 Professional SP1 32-bit CPU Intel Core 2 Duo E6600 2.4GHz, overclocked to 2.7GHz Motherboard Asus PL5D2 Memory 4GB DDR2-667 (4x1GB in dual-channel config) Graphics Card nVidia GeForce 9800 GT Sound Card Creative X-Fi XtremeMusic Monitor(s) Displays Acer Screen Resolution 1920x1200 (DVI)
Keyboard Standard Mouse Microsoft wireless optical mouse PSU Antec TruePower 2.0 Case Cooler Master Centurion Cooling various fans Hard Drives OCZ SSD Vertex Plus 60GB SATA (Firmware 3.55), 64MB cache
Hitachi HD321KJ SATA, 320GB, 7200rpm, 16MB cache Internet Speed DSL; ~330KB/sec down, ~110KB/sec up Other Info Have a laptop too :) (Compaq CQ60 also with Win7 Pro SP1 32-bit)
Drives in both systems:
C: - Windows 7 + apps. Pagefile is fixed size and located at the very end of the partition.
D: - various temp files/cache for Firefox and apps/games.
E: - videos, music, misc. storage, torrent downloads, etc.