I need help because i want to buy a Registry cleaner Because my computer is running slow but i dont know what to buy

1.Clean My Registry

2.Registry Fast

3.System Mechanic

4.Registry Mechanic

5.Advanced Registry Optimizer

6.RegCure

I have 3 different Registry Cleaners (Registry Mechanic 6, System Mechanic 4 and Registry Cleaner) and each one of them found different problems with my registry. Which one should I believe?