slow computer

Hi,

I hope someone can help me as I am ready to toss this computer out of window--this time for sure.

Just had reformat done, got it back 2 days ago, and it ran great. Now, here we go again!! It's slow again but not as bad as before reformat. One program said a registry change had been made to C:WINDOW\system32\rundll32.exe. I do not understand a lot of tech issues and don't even know it this registry change really occurred or if it's okay registry change. I just hope you can help assist me.

Thank you