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There's a whole bunch of answers with different solutions. Work your way through and hopefully something will get rid of it.
As for your Q's. This is my own personal opinion;
Q1. Paid software will most definitely be better, provided it's a real service and actually worth it. But that's not to say you can't find free software that's better.
Q2. Not all software fixes any problem out there. All the viruses that get created today can wire themselves into a system so much that it becomes extremely difficult for software to safely remove them.
So usually you end up trying a whole bunch of different removal solutions before you hit the right one that does the job.