Yet another case of Steam’s PC client giving me headaches that can’t be solved by mere mortals.  I don’t think I’ve had  ONE successful launch day download that didn’t require 2+ hours of fixing/waiting/etc.

Left4Dead2’s new DLC level “The Passing” added one more mission and several new gameplay modes on Thursday last week (which was free on the PC, but cost money on the XBOX).  I forgot to leave my machine on during the day of launch, so I had to start downloading when I got home from work.  My bad – but I was surprised that they didn’t let people start pre-loading like they did for the original launch of Left4Dead2.  Anyway, after getting several ‘Servers too busy – try downloading later’, I finally got a download started.  4 hours later it completed. Steam restarted to install some patched, and then when I restarted Steam, my Win7 x64 popped up a dialog saying it was going to apply compatibility settings to steam because it detected an install problem.  There was no way to say “No – DON’T do that”, so it went ahead and applied these ‘settings’.

Then, when you tried to start Steam again, you got error dialogs from Steam saying:  “Running Steam in Windows compatibility mode is not recommended. Please remove any Windows compatibility settings for all users under file properties for Steam.exe and restart Steam. Press ‘Cancel’ to permanently ignore this warning and continue.” I click on the file properties for the executable and go to the compatibility tab -but it says there are no compatibility modes set.  I try setting/resetting them – still get the error.  I look online, people have tried completely installing/uninstalling ALL their games/Steam – no luck either.  Finally, someone grabs Microsoft’s Application Compatibility Tool and found the compatibility keys for Steam.  He then dug around in the registry to find where those keys were kept, and does this:

To fix the issue:

1. Hit start->run->regedit
2. Go to key: HKEY_CURRENT_USERSoftwareMicrosoftWindows NTCurrentVersionAppCompatFlagsLayers
3. Look for a entry with your path to steam.exe
4. Delete that entry
5. If you dont find it there try HKEY_LOCAL_MACHINESoftwareMicrosoftWindows NTCurrentVersionAppCompatFlagsLayers

So, there’s your fix