Most of viruses invade through utility programs, so it can be treated using vaccine programs. We should install the proper vaccine program in advance, and manage to keep up with the latest updated version. By the way, if operating systems are infected, it is very severe. PCs (pl) cannot be turned on properly. We should boot the computer through an emergency way and execute the curing program. In some cases (pl) we can get the help from professional engineers.

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We have 2 ways of "most" things
1)For general groups: "Most ____" ---> Most students study hard.
2)For specific groups: "Most of the _____" ---> Most of my students study hard.

Remember: plurals for general statements
--> PCs cannot be turned on.

Emergency
I think you meant emergency, not emergent
Emergent--(adj) coming into ---> The emergent countries of southeat Asia are popular tourist destinations
Emerge--(v) to come into; to come out of ---> Emerging out of poverty is possible with a good education