Heyyo,
I remember before hearing that punkbuster supported the HL engine... first off, if this was even true, why the heck did they stop? punkbuster's probably the best anti-cheat system made. Works great on the Battlefield series, SOFII (<< uber-hacked game.. really needs PB on all the time or I'd die.), and a couple other good titles.
Yeah, CD's nice, but it sucks how the clients have to have it installed n' running on your comp for it to work... at least for games like BF series with PB you just click "enable" and then never worry aboot it ever again.