1) a list of Commands can be found here
. if your looking for a specific one let us know what you want to do.
2) Yes and No. Will reinstalling Windows wipe your Linux Install? Possibly (actually very likely if they are on the same hard drive). Is Microsoft out to kill OpenSource and GNU software? We dont know. MS is making moves on both sides of the board here teaming with Novell and suing for copyright infringement at the same time.
3)You will most likely need to install DirectX using Wine. although I'm not sure.
4)Suspend is like Standby. Hibernate is like Hibernate (its on a separate menu in Windows that you can acess by hitting ctrl(?) when acessing the shutdown window). Suspend means to Suspend to Hard Drive and Hibernate saves all your settings and shuts the computer down in a way that allows for faster reboots.
5).deb files will open in KPackage and install themselves just like installers in windows. Automatix2 offers your Codecs for MP3,WMV and other non-free (proprietary) file types. and many other programs. (Follow the Kubuntu install instructions for Automatix2 otherwise it will not work right)
Make sure you enable all the Repositories. See the Ubuntu Forums
for how to do this. (There is close to 3,000 packages available for ubuntu in their Repos alone)