I bought an entire new PC for HL.
PII-350 (spanking new100Mhz FSB, not the old and slow 66Mhz)
128Mb 100Mhz RAM,
ATI Xpert 98 AGP card (AGP and not PCI, and no passthru 3d card required)
6GB HDD
14" 800x600 CRT.
Cost me £1,500!!!
I remember playing in the dark and ****ing myself when a headcrab jumped out of the dark! Once I'd finished I found Counter Strike Beta and TFC on 56k as I couldn't get ADSL or HomeHighway in my area. Ended up play Counter Strike until Source, setup and admined a bunch of server then I quit for the Battlefield series.