Re the games Q, you will have to install the game to the new pc, for the reasons you mention above. However, if you look in the folder the game in installed to ie d:\serious sam 2\ somewhere in the subfolders there will be a folder called savedgames (or such like). Copy all the files in this folder to cd/dvd/ext.HD.
When you've installed the game to the new pc, just reverse the procedure and copy to the new pcs savedgames folder, (you may have to create this folder as some games do not make it untill a game has been saved, so make a note of the exact location/name of the original.)
Data can be transferred from pc-pc but actual applications such as word/games often need to be installed fresh to allow the correct entries into the reg.
Hope this helps.