My MacBook Pro has a 500GB solid-state drive. (Technically 512GB, I suppose, but it reserves all the rest to replace blocks as they fail. I’m okay with that.) When I first got this computer, I decided to allocate 380 gigs of that to Mac OS, and the remaining 120 gigs to Windows, because I like being able to dual-boot into Windows when I want to help someone with Windows or play a game.
Turns out that I don’t use much storage on the Mac side; I prefer to keep most of my data on my desktop, where it’s more secure. But meanwhile, Windows games are big and I have a bunch of them (darn Steam sales), so I was running out of room on the Windows side.
So I decided to shrink the Mac partition and expand the Windows partition, to give them each 250 gigs.