To simplify backing up a laptop (Windows Vista), I'm planning on sharing its C: drive (with password protection) and using that to back it up from another computer.

What are the security implications of this? If I share C: with a reasonable password, how big is the risk of compromise if the system is e.g. inadvertently used on a public WLAN or similar?

Background:

I'm planning to use [Areca Backup][1] to back up two systems (Windows XP and Vista). My current plan is to install Areca on the XP box, and share the Vista system's C: as a shared folder, so the XP system can read it.

Then I can set up the drive as a network drive and have Areca read it like a local drive.

Of course, if you can think of a more elegant way of doing this, I'm open to suggestions.