Windows 7: Change default game save location

I heard that the Windows standard is for games to save files to C:\Users\<Username>\My Games\<Game name> and many of my games (Oblivion, Prototype, etc) follow this standard.

However my C: drive is a 128Gb solid state drive for the operating system only. All my games and files are stored on my 1Tb D: drive and I want to change the default game save location to somewhere on D:.

Last time I formatted my system drive I was gutted to find that despite saving the game information on D: I had lost my saved games. So if there is a way to change the default game save location I would be grateful to find out, thanks!