I want to the command history to be saved in viminfo so that when i restart vim the next day I still have the previously entered commands stored.

What I've been doing is just leaving vim open for weeks at a time, which leads to it running slower and slower as time progresses.
Plus, I'm still screwed if I need to reboot, or some other event occurs that results in vim getting shut down.

I'm pretty sure I figured out how to set the options for this...
however, when exiting gvim, i get the message "E138: Cannot write viminfo file C:\home\chris\_viminfo!"

Why would this be?