Right... that "share" has everything to do with Local Area Network sharing... it is by default for several reasons, 1. because the setting hasn't been changed since the first Windows XP release.. and 2nd because Windows XP was meant as a Local Network Operative System... as for the Home Edition, I wouldn't know if it's also set by default, but if it is, it's probably because the Home Edition is a variant of the Professional Edition.
On a home computer that's not in a Home Network, you can also disable other Services like:
Remote Assistance Service and all others referring to Remote Assistance, also other services like; Computer Browser, Server, Telnet, Telephony, Messenger, and Remote Registry... and from the Control Panel> System>Remote> disable; Remote Assistance and Remote Desktop. You may also search the Net for other Services Configurations to secure your system against intrussion.
A reliable Services Profile is
Black Viper’s Windows XP x86 (32-bit) Service Pack 3 Service Configurations. See from Safe, to Bare-Bones and apply your prefererred Services Profile