All day I've been fighting with this. I couldn't install to my D drive (I can't use my C, as it's a Solid State and used primarily for windows-related programs, so I have no room.) So it was installed on a second HD that I use primarily for games.
Fast forward to me installing and REinstalling over and over, I finally just installed Forge (and Optfine) to the C drive and changed the directory to Forge and Optifine to the D drive, copied the C drive's .minecraft folder and pasted it to the D drive.
I can get Optifine to run just fine, by editing the location on the profile.
Forge, however.... I can't. It starts to boot, reads 4 mods, then insta-crashes.
Hopefully this text log is in the right place, forgive me if it's not, this is my first post.