Suspicious long list of names in Credential Manager - Help!

I was peeking around in Control Panel, Credential Manager, and found a long list of names. It states: Store credentials for automatic logon, then Windows Vault.

Under "Windows Credentials" there is a long list of names and all were modified on 5/8/2011. There are about 40 of what looks like computer logon user names.

Examples: Brad-PC, KickAss, Hollywood-PC, MATTS-LAPTOP, MEDIACENTER-PC , Owner-PC, SARAHS-LAPTOP, etc.

When you click on each of these, they look like this:

Internet or network address: Brad-PC
User name: Brad-PC\HomeGroupUser$
Password: ********
Persistence: Local Machine
Edit Remove from vault

This is very suspicious, as I have no idea where this all came from. There has been suspicious activity on my laptop lately, so I was peeking around a bit and found the above info.

Why are those users on my laptop?

Thanks