Publishing a *.msi package!

I’m doing some lab work in preping for the 70-219 exam. I tried to publish a msi package and link it to the default domain GPO. 1st I created a share and then put the msi file in the share I just created. 2nd I edit the default domain GPO and published the package to everyone. (When I did this, Windows displayed a warning message that it could not verify that my folder was a network share. D0 you want to continue, I chose yes) 3rd I went to a Professional machine and tried to install my packagethrough the Add/Remove programs. When It went looking for any programs on the network, Windows could not find any. I can see the folder as being shared on all my network PC, enen downlevel clients. What did I do wrong?