This is not a general problem on Win7. There is no significant difference in the speed on the different Windows versions. Then we would have been flooded wiht similar reports and we did not have any. I have been using SQLyog on Win7 since it was released.
Also I doubt that any 'powertool' has any influence on this.
Somethings happens on your system that does not happen on most systems. I would first try
1) perform a virus/malware scan with a quality AV scanner
2) temporarily turn off AV software – just in order to check if there is some blocade there
3) check in Task Manager (or any performance monitor) for any information that can give an idea.
4) try to close background processes that are not required in order to see if there is a conflict.