It would help to know what sort of infection we're dealing with. The most common type of late that will not allow an internet connection is Win Anti-vir or Win Antivirus 2011;  both are boot sector bugs that pretend to be antivirus/anti-spyware tools.One nasty feature is that every time you reboot your pc, the infection spreads to other sectors until you suffer a total system freeze.

I believe Antimaleware from malbytes is supposed to remove the infection, and so is Spyware Doctor. If the damage has already reached critical limits, you may not be able to install either program, even in safe mode. Your only remaining option is to format the hd and do a fresh Windows install.

Good luck.