Truecrypt is cross-platform, it works on all Windows versions, but it's not full-disk encryption. It creates encrypted virtual hard disks that are stored within your unencrypted hard drive. You should probably be looking at Bitlocker or something along those lines for full disk encryption (imho, it's much more secure and probably easier to just install linux and use the default encryption offered, no backdoors like Bitlocker is known for. Use a dual-boot if you really need Windows for some things, but linux should do just about everything)
Search "Bitlocker backdoor," there was a huge controversy about the FBI trying to compel Microsoft to put in a backdoor. Supposedly Microsoft refused, but personally I doubt it. I mean, if there was a backdoor, they would never admit it, nobody would use their crapware if they did lol IMO, stay the hell away from anything that isn't free and open-source if you want real Fed-proof security. That means nothing at all from Microsoft, Google, Apple, Adobe, etc. Linux/BSD are the only options there are for that. If you really need Flash to watch something or Skype, keep it to a VM and you should be okay
TC can make FDE, and you can encrypt entire OS and even can embed hidden OS in it. However, it doesn't officially support Win 8.x, and if your machine use UEFI+GPT, it will cause problem. You can use file container w/out problem on Win 8.x, and if your machine is old and use BIOS, then probably you can encrypt OS too.
