Is there a specific version of xDebug I should install if I'm running PHP 5.2.10 on my Linux box?
The Windows binaries generally work for every mini release for the mentioned PHP version, although the extension is built against the most current PHP version at that time. The VCx marker tells with which compiler the extension was built, and Non-thread-safe whether ZTS was disabled. Those qualifiers need to match the PHP version you're using. If you don't know which one you need, please refer to the custom installation instructions.