What are the bad effects of computer virus
the worst case, it will destroy you all your software, then send it self to your friends and destroy their machines and so on. till there are no more computers left. then you get the pain in the a$$ virus, it does nothing but bug you with useless pop up msg. search for AVG.com, download a free anti-virus, keep you fairly safe.
and also, it can stop your pc from loading up, which has happened several times on the crappy pc downstairs, argh so many people messed it up. avg is a good antivirus :D
it can hack into your fridge and steal your food
Total freeze / lockup.