Question : Problem: Mac Titanium Powerbook G4: Ventilation fan

I purchased my Mac Titanium Powerbook G4 (500mhz), used, about 3 months ago and have used it almost daily since then.  This is my first laptop and I'm still adjusting to OS X after a year on a PC.

The mac has been sitting flat on a tabletop, with the power cord plugged in; the battery is in the computer.  Three days ago, for the first time ever, the fan kicked on.  Scared me to death, as it was accompanied by a slight burning smell.  I quickly shut down and the sound stopped.

I felt the bottom of the machine and it was hot to the touch, especially the right side (the battery is on the left).  I have since raised the edges of the computer on books, for better ventilation and was told (by the previous owner, who I called in a panic) that Apple sells something for this purpose.

My concern is: the ventilation fan has kicked in several times since the original occurance.  And the machine is always awfully warm.  Is this normal?  I find it odd that the fan never kicked in before this and now has done so several times in a few days.

Twice the fan came on when I was online and my browser froze; I was using Netscape 7.  The other time I was running Norton Antivirus scan. I suspect the freezing was due to a pop-up, cookie, or some other animated micro that was trying (without success) to download because the colored wheel kept spinning and I was able to use other applications, only Netscape remained "busy/frozen" and required a "force quit" to exit.  Is there a connection?

Any help would be very much appreciated.
Arlyn
PS: first response was helpful and i've added additional info, but remain fearful of my fan and its sudden appearance after so much quiet.  And yes, it does sound like a hairdryer!

Answer : Problem: Mac Titanium Powerbook G4: Ventilation fan

The 500's (actually all Rev. As) are notorious for running hot, my 667 (pre DVI) does not seem plagued by that problem, but my fan has always kicked on during intense application use.

For starters, when Cpus get abnormally hot, their processors tend to get glitchy, which could explain why you're having lockups.  I would try to rule out a software problem before panicking.  Maybe an archive and install in OS X?

If after an archive and install, you're still having lockup problems, i'd think about having apple look at it.

I would also be concerned if the burning smell comes back.  The initial smell may well have been from the fan not turning for quite a while.  When it finally kicks on, it pushes dust around, and it can settle on hotspots inside the laptop.  

A personal warning, the 500's had numerous problems that are quite common.  You may well experience paint flaking problems.  Also, take great care with the hinges, i know that there have been problems with the Rev A., and it can be quite expensive to replace...