I'm in the process of getting W10 running (which is a bit of a mission) and I have a few instances of Windows - some W7, some W10. When I change OS's it always says "your recycle bin on drive X is corrupt do you want to empty it", usually for more than one drive (I have 5 or 6 drives).

1) How do I stop the messages? Or should I not bother?
2) There's a system volume information directory of unknown size, and recycle bins. How do I ensure they're only taking as much space as is required for one OS?
3) Are there any general recommendations when moving between OS's, or running multiple OS's over one drive?