hl2.exe has stopped working. How to fix?

I had a similar problem, but it would occur on about 50% of map changes. The problem is that Vista is often picky about how much of your RAM and virtual memory can be used by an application. In TF2's case, Vista sometimes doesn't expect to suddenly go from the most CPU-intensive part of map loading, to the lightweight part ("Sending Client Info") and suddenly jump back to loading the precached models and map.

Having better computer hardware seems to help the situation somewhat, but either way you should try the following:

(The thing all URLs start with)support.microsoft.com/kb/940105

^ This update seems to fix the problem for most users, but I found success with the following:

- Go to your computer's Display Settings, found under Personalization in the Control Panel.
- Open the Advanced Settings. Find the tab which allows you to see your monitor's refresh rate. Make a note of this number.
- Right-click on TF2 in the Steam window, go to Properties, then Launch Options.
- Put the following into the text entry box: -refresh XX
(where XX is your monitor's refresh rate in Hertz).

Setting this will ensure that TF2 doesn't try to exceed the refresh rate of your monitor. This is most useful in cases where you are using an unreliable graphics card (and if this IS a graphics problem, go find the latest drivers for your card). There's a whole lot of other reasons you could be experiencing these crashes, but we would need to know more about your hardware and what programs you run alongside Steam to be more helpful.