The NCAA has made some changes to its online tournament streams for 2012. Deadspin has the rundown.
To watch games online, you'll have to authenticate yourself as a cable subscriber, usually by entering the account number on your cable bill. Be sure to have this info handy before you leave [for] work Thursday morning. If you do not have your account number, or are not a cable subscriber, you'll have to purchase an all-access pass to March Madness Live for $3.99-which also lets you watch on your phone or tablet.
All tournament games airing on CBS will be available for free online, with no need for authentication.
To recap, if you are a cable subscriber, you are good to go. But be sure to remember to bring your account number on your cable bill to work tomorrow or you'll be S.O.L.
If you are a satellite customer, instructions are here. I haven't tried these so I can't vouch for them, but Backing The Pack has got you covered.
Enjoy the Madness!