Alpha 1 and Issues with WinXP
First, I want to send out thanks to both Innocence and Jason for their invaluable help determining the problems the Launcher is having with WinXP. Without their exceptional help, we wouldn't know anywhere near the amount of information we know about this issue.

The Launcher relies very heavily on several functions in the WinAPI dealing with how files are stored and how window handles are in memory. Unfortunately, it appears that WinXP handles these functions entirely differently than the rest of the Windows family.

First off, WinXP appears to want to update files that don't particularly need updating. As far as we can tell, all the stats that are checked on the files are correct on the WinXP machines, but for whatever reason, at least one of the checks is failing, and the files are being redownloaded some of the time even when they don't need it.

The second issue involves the actual Launcher executable. You can't erase or modify an executable that is currently running. To get around this problem, the Launcher, when it detects that its own exe file is out of date, downloads a replacement from the server called LauncherTemp.exe. It then exits, and a secondary program runs to erase the old version of Launcher.exe and rename the replacement. WinXP, for some reason, will not delete the old version of Launcher.exe. I think this is not a critical failure, because it then goes ahead and replaces Launcher.exe with LauncherTemp.exe anyway. But you will still get an error box, which is annoying.

The next issue involves handles. It's a bit complex, but the idea is that once the Launcher starts the Client and exits, the Client itself is required to wait for the Launcher to fully exit memory before it can start any serious work. To do this, it checks the handle of the Launcher. WinXP, however, fails to find the handle from the Launcher. This is a game breaking bug for WinXP users, because the Client will exit on hitting this error. Now, on one version of WinXP, this happened every single time, on another version, this bug wasn't detected. This could be a localization problem more than a WinXP problem.