Convenience, Relative Paths, and Dropbox

I'm looking for an easy/automated way to keep data current and redundant across machines. I use mostly portable apps on

a) a thawed drive of a work computer with Deep Freeze on the C: drive
b) a home desktop
c) another, older laptop
d) a 140G USB/Firewire hard drive
e) a USB stick (or two)

In terms of programs, I sync folders every few days. (Mostly Firefox, when add-ons update.) What I really want is a way to sync at every use the small but vital data, say from OpenOffice, or Evernote, or Freemind Portable, as examples. Or better yet, the data files from Foxnotes. (I realize not all listed are in PAF format.) I know that many programs use relative paths, but I am loath to trust them, if drive letters are changed. I think that Dropbox Portable has relative paths. Is it easiest to shift all these programs so they save to the Dropbox folder, or set up Belvedere or some such to copy programs, or what? Any suggestions?

BTW, Dropbox sees the PA.c "Documents" folder as a system folder, and won't let you sync it.

Thanks in advance, I hope I picked the right forum.