Problems with Half life running on Win 2k

[Brian07]

I installed half life just fine on Win 2k. When I click the icon to play, I get the pop up, service pack 3 or higher required to play half life. The same win 2k disc is installed on 3 computers here at home, this is the only one puking.

P3800
Win 2k Pro
Asus P3V4x
256 megs PC133
Geforce 2 Creative
SB!Live

300 Watt ps

Any ideas?