One computer left standing.. help please :)

My children downloaded logmein hamachi (they are 10 and 11) with someone from ?? another country) while playing an online game and since then our wireless network has been hit or miss with random IP reassigning. I uninstalled the software. One computer has completely crashed beyond saving (It does not even recognize the hard drive) There are browser popups on firefox whenever it loads and encrypted files that have been loaded on the computer. These cannot be scanned by the antivirus program. Our wireless devises are still not connecting to the network.

Sigh.... Where to start....

MBam would not load.. otherwise... I have run ccleaner and tried my best to follow the directions.

please tell me what you need me to run. thank you.