With the Windows7 PC that you turned off Network Discovery, it will no longer be able to share, but the other PC's in the network should. Network Discovery has to be ON to share and to see the other PC's in your network, however the other PC's should be able to see each other and share.
Are you having problems with the other PC's sharing now or just the Windows7 PC that you turned off Discovery? If your having troubles with all PC's sharing now, Shut down all pc's and reboot the router by cycling the power off and on, then turn on the PC's and check sharing.
Relating to Windows7 Network Problem:
If you turn on network discovery on all PC's, did you run the network setup wizard on windows7 and name the homegroup the same as the network name on the other PC's?
When you setup a home network, its best to temporally turn off firewalls so they don't interfere with the setup process and prevent the connections. Then after you get it all tested and working, turn firewall back on, and retest. If you now have a problem, its most likely the firewall blocking access.
In the setup of the network, did you choose "home/work"? The PC's that are going to share, need to be on the "Home/Work" network with the default windows settings in order to share. In the Advanced page that you went into to turn off discovery, you'll see that there are 2 groups and different settings for both the home/work and public, check that your changing the settings for the right group.
It's best to leave network discovery and file/printer sharing OFF in the Public Profile. You want to keep the Public profile as secure as possible for when you connect to networks outside of your home network or want to easily stop sharing on a PC. All you would do is switch to the public profile to stop sharing access. The Home/Work Profile should be the one where you allow network discovery & file/print sharing ON. Thus you need to be on the Home/Work Profile for sharing.
Its hard to know how much some one your trying to help knows about PC's, sorry if the above is all redundant. Some more details are needed to know what your having problems with and your complete network setup if the above doesn't help. Look over all your settings carefully and check with Windows Help & Support, ...sometimes it IS actually helpful, lol.
Hope this Helps, Good Luck