Recently I bought new computer, with small SSD harddisc and large fixed HDD. The problem is that I want to sync the whole Dropbox here, but the SSD disc is to small for it. I solved it by hardlink of Dropbox to HDD - it means, the Dropbox folder is still in my Users account, but physically the data are in D: harddisc.
How to do it, step by step:
mklink /J C:\Users\Zeleny\Dropbox D:\Zeleny\Dropbox
Note: seems like it's possible to sync Dropbox also to network drive, but it needs special hack: https://gist.github.com/pavank/2961448