Ubuntu is great. Its linux so it has high security. You should install it in a VM first. Then dual boot if you like it. It comes pre-bundled with a lot of programs
2.) Open Office
3.) Software Center
4.) Torrent Client
You should use the 32-bit version of Ubuntu. Since Linux has the PAE kernel which allow a 32-bit OS to see more than 4gb of ram. And also, Flash Support stinks in Linux 64-bit. It works, but is not the greatest. Adobe released a beta for flash to run on Linux 64-bit. But I still recommend using 32-bit.
Just download the 32-bit ISO from Canonical. Burn it to a CD, then navigate to the CD. Open up Wubi.exe. And select install inside windows. Then after that is done, reboot, select Ubuntu for the Windows bootloader. Then the Ubuntu install will complete.http://en.wikipedia.org/wiki/Physical_Address_Extension