Left 4 Dead - will it run?

Hey Guys,

Title says it all really, i have the game on Xbox, but for many reasons i won't go into, I'll probably be picking up a PC copy when it dips down to 20$ on steam, anyway, I expect it will run at a playable rate at high-ish settings.

Here are the important specs

- Intel 945G motherboard
- dual core 2.8 GHZ pentium D 820 processor {smithfield architecture}
- Sapphire HD 4650 GPU, 512MB of gddr3 video RAM
- two sticks of ddr2 RAM, at 512 MB each

I can run multiplayer source engine games with almost all settings maxed out and still get decent framerates, but the snag here is that Left 4 Dead has your computer render more enemies then other source games.

So can i get at least medium settings, maybe with a bit of Anti aliasing/anistropic?