When the amount of free space in the Finder is more than one megabyte, the Finder displays the free space in megabytes. I like it to keep displaying in K. This will force the Finder to display always in "K", not "M".
Launch ResEdit and open your copy of the Finder. Open the CODE resources. Click once on resource number 23. Go to the "Resource" menu and select "Open Using Hex Editor..." (don't double-click on it since you might have a fancy CODE template installed in your ResEdit, which would make the next step possibly impossible [don't tell my old English teacher that I said that]). Click Yes if it asks if you want to decompress the resource.
Use "Find Offset..." to go to offset 18E. You should see
0C86 0010 0000 6500 0082.
If you don't, don't continue.
Change the 6500 to 6000. That is, change:
0C86 0010 0000 6500 0082
0C86 0010 0000 6000 0082
Quit ResEdit, saving your changes. All this patch does is change a conditional branch to an unconditional one. In other words, whereas the Finder used to say, "If the amount of space available is more than one meg, display in M; otherwise, display in K," it now says, "If the amount of space available is more than one meg, uhm, display in K." Trust me; it really says that. Listen closely next time.