First question I read on hear that pertained to my problem: "I am using a G4 Powerbook 1.33GHZ OS.X 10.4.11. I have Techtool Pro (4.1.2) constantly monitoring and recently it told me that I have an incorrect valence (error msg -61) on my main drive. Now I have checked the Techtool database and it says two critical things. One, don't ignore this message - the second is that it pertains to a Volume Error, and that if running Techtool Pro does not fix it then it probably is serious. Great! what I can't ascertain is what to do about it. For example, would reinstalling Tiger fix the problem? Is it hardware related? Does anyone have any clues please? Cheers, Rob" The answer he was given: "No, that is a last resort only. Boot off of you Tiger DVD (or the one that came with your computer). After the first screen where you select "English" stop there. Go to the Utilities menu and select Disk Utility. Select your MacOS volume on the left and click on the First Aid tab. Now click "Repair Volume (Disk). After the repair is done, click the Verify button. You may want to consider getting Alsoft DiskWarrior as it is much more complete in doing disk/volume repairs than Disk Utility. In many cases, it can fix problems that Disk Utility can not." My Question: I have a Powerbook G4 running Panther OS 10.3.9 I don't receive the entire warning that was pictured in the prior thread ? RE: this ( http://forums.macrumors.com/showthread.php?t=508059 ), just the Incorrect Valence (-61) from Tech Tools.... will the fix described for Tiger also work on my Panther 10.3.9 Powerbook? Also- can I upgrade to Leopard straight from Panther, or do I need to buy all of the newer versions to get there? (I'm hopin' to be able to have someone at the Apple store do that, as I don't have alot of $$ to upgrade...) I'd appreciate your help- Thanks The answer I got: "It sounds like the valence band in one or more of the transistors in your CPU is incorrect. That can cause the Fermi level to be off, which might make the transistor(s) not function correctly. If the Fermi level is too high or too low the transistor may not operate correctly. It might act like a diode, or even just a resistor. To fix the Fermi level and correct the valence band, you may have to dope the transistor with either some Gallium or Arsenic impurities the the transistor in question. You will need to figure out if the incorrect valence is in a N-type region or a P-type region, and whether it is too high or too low. Maybe the Tech Tool log will say? Then you need to actually deliver the dopant to the transistor, which requires a mask with a 45nm feature size. This should go without saying, be careful with the dopants. Arsene gas is so toxic that a concentration high enough to be detected by smell will kill you (though I'm curious as to what it smells like. If you somehow find out, please let me know)." Can someone please tell me how to fix this problem myself (if possible), or if I have to consult a chemical expert... The Tech Tool error message only states: Incorrect Valence (-61) Thank you in advance for any plain english help.