question about internet cable, if two are on the same service can a IT person access my info without consent?

Any one can, this is considered Cracking, it shouldn't be easy if you do all windows updates, have a firewall and antivirus. if you have no antivirus i recommend AVG Free edition and for a firewall i recommend Zone Alarm Free Edition. Keep in mind though that not the average user can crack in to a system.

If you have a anti virus /firewall..Still possible but a little harder than most "Average Users are going to be able to. NAT (Network Address Translation) Hardware router ..Even harder I recommend. you use a "Layered approach to security (Remember there is NO push button automatic solution to security) use a NAT router an anti virus and software firewall on your desktop. Also Unless you are using your connection a a LAN (Local Area Network) connection go into you network settings and turn off Client for Microsoft networks, File and Print Sharing and Net BIOS (This is called "Unbinding TCP/IP this effectively turn off all file sharing to the modem (and Unfortunately if you using it to transfer files from machine to machine) this layered approach has worked for me (And the company I use to work for) it is kind of the "propeller head approach" to security but it seems most effective

Generally on a well configured network and administrator has full access to everything. This is to allow monitoring against illegal use, and to allow rapid interaction when something goes wrong.

no this person cant unless he is a hacker!