What hapens if you lost your half-life install disk?

I lost my install disk :cry: but i dont know waht too do is there somewhere can i download it and then put in my cd key?Im a great player in esf but since my bro had to renew are computer and all taht stuff we lost it.We can get it back if you know where i can dowload a half-life version that allows me too play it and i can put my cd key in.If you know tell me that would be great.

The CD Key is the important part, if you had lost that then you'd be out of luck. So... lucky you. =P

Download Steam and give it your CD Key. Installing from the old CD would set you up for WON, which is a dead system. Steam is the current platform for playing Half-Life over the Internet, and your valid CD Key is enough proof of ownership for Steam to start setting Half-Life up for you.