Hello Lynne, my name is Dan.
I will do my best to help you, the only stupid question is the unasked one.
Have you used Disk Utility to repair the hard drive when booted from the installation disk?
When you used TechTool did you rebuild the directories?
What version of MacOS X are you running?
I like TechTool but I use Disk Warrior more, it doesn't do as many things as TechTool but what it does it can't be beat.
I do recommend doing the TechTool while booted from the DVD/CD for TechTool or Disk Warrior.
Might give a SafeBoot a try.
To do a Safe Boot, restart and before the first chime press and hold the 'Shift' key.
Wait until you see the Apple logo and the spinning gear appear, then let go.
It can take as long as 20 minutes to load, so please be patient.
When the login screen appears it will say in red on the login window 'SafeBoot'.
Now login and give it a few more minutes to finish loading.
Try doing whatever it was it was giving you the problem. If it works then probably the problem is solved, so restart normally.
If the problem persists then restart normally also, other fixes will need to be done.
Let me know what you think.