I think this issue is not so simple as a lot of people running HL2:EP1 might believe it to be.
My PC is ok, it's certainly good enough to run Half Life 2 and, with HDR turned off, Lost Coast will run without any problems. My specs are as follows:
A64 3200+ Winchester
1Gb Crucial DDR400 CAS3
ATi x700 Pro 256Mb PCIe
Admittedly the x700 Pro card is the weak link in the system but it runs the game fluidly at 1280*1024 with the settings up full, except for HDR, which I turn off. The problem is this:
In the section after Gordon and Alyx are thrown into the citadel by Dog, you pass through an archway into the next section of the game. Alyx says something about not being able to believe how bad the damage to the structure of the citadel was, but after about a second or two of this the game crashes. I turned the display settings down and the game no longer crashed. My conclusions are:
1.It is highly probable that Episode 1 may possibly use larger textures than Half Life 2.
2.Episode 1 is not as stable as Half Life 2.
3.It's not necessarily the processor on my graphics card that couldn't cope with the game, it's not the amount of onboard GDDR, it's got to be something to do with the overall bandwidth of the buses in your PC.
I believe that the model of Alyx Vance is a higher quality one in Episode 1 than it was in Half Life and I know that there are extra-high quality settings available to people running the game on PCs with graphics cards, RAM and CPUs much faster than mine, but surely the point of the survey they let us take on Steam would be to make this game stable on lower-end systems too?
Don't forget that it's very possible to run HL2 on a Radeon 9800, a Pentium 4 that doesn't necessarily run on socket 775 and with 512Mb of RAM. I don't see why Episode 1 should crash at this point in the game, especially when there's nothing going on on-screen at the time.
I refuse to end this post with recommendations for any of you to upgrade from a HL2-worthy system just to play Episode 1. I'm afraid it's part of the software design process not just to analyse the software's aim, not just to code it and make documentation, but to fully test it as well, and I think that we, as games players, forget that we should demand this just as much of our games as we would of any other product we purchase.