Dear Lazy and/or Uninformed People,
In order to view video files, there are a few things you need to do with regards to basic computer maintenance. You should defragment your hard drive once in a while, as opposed to never. This will allow your computer to function much quicker. Think of it as organizing your closet and then trying to find a tie, much easier after you've cleaned, no? Run a program like Ad-Aware or Spybot S&D to remove malware and such that can slow down your system. Clean up your start-up and taskbar-running programs. If you run a shitload of programs in the background, it's going to eat up system resources, which are useful for tasks such as video playback. Run a virus scan, it is quite helpful to not have a virus on your computer. On a related note, don't use garbage software like Norton Antivirus, it is a piece of shit and will slow your computer down immensly, especially on older, slower systems. Try something like AVG antivirus, much better program. Basic computer maintenance can go a long way towards resolving common problems, such as "I hate mkvs (read H.264) they are shit and never work."
As for codecs and players, the best thing to do is to get the CCCP codec pack, which comes bundled with Media Player Classic. This has nearly every optimal codec and the best player in one convenient location. The only exception being CoreAVC for H.264, sop get that if you need better playback for the format. There is no reason not to take the small amount of time necessary to familiarize oneself with basic knowledge, and it will be very beneficial if you plan to continue watching fansubs or any video files for that matter.