I want  report a bug.

I have I7 gen3 processor, in msconfig I go to boot->advanced options->number of processors-> I select 8. After a restart my computer work like a pentium 4,it was hard to make a mouse move,programs open very slow. For other user with same problem to fix that just unselect checkbox in msconfig []number of processor and make a restart. 

I tried your method and I do not get your problem. I do not see why you need 4 cpus for booting up your system. This is only for the system to boot with all 4 CPU and nothing more. Remember 4 of those are virtual. Maybe you need to enable VT in bios.

I don't recommend using all 4 cpus to boot your computer. The OS will assign resources to other cpus to load balance when syn enabled.

Colakid not your problem! I don't ask answers, just I reported a bug.

Anyway I fix that with bios update. Mobo Asus p8h77-v.

why did you do this? There is no benefit in setting it to the highest value.