No, you really don't need to be worried about it. They're scanning for IIS exploits, they really don't apply to you
I run a webserver and get that alot, its mostly just script-kiddies looking around for an *easy hack*. Maybe jot down the ip that the scan came from and keep an eye out for other scans from the same general IP address. If it gets to be a problem bring it up w/ the ISP.
If you start seeing apache specific exploits then you should start being a little more worried. Just keep an eye on your secure and message log files for unusal stuff.
All in all your fine tho. You'll probably see alot more of those.