Dell inspiron 9300 getting hang or restart after every 15 min

You cant get in safe mode because the PC hangs before windows ever try to start.

Try to press F8 multiple times but right after the Dell screen.
Some computer don't like that you press F8 while the bios is loading and just hangs there, maybe its your case.

Call1-800-WWW-DELL

first thing to do is run psa test. turn off laptop. remove batt use ac adapter alone. press and hold on Fn key then press power button once. complete the quick test check if you will be getting error codes like 0142 , 0146 this is hard drive replacement.

Please try to upgrade the BIOS version and flash the BIOS. Please check the link and follow the instructions: http://support.dell.com/support/edocs/systems/ins1525/en/SM/bios.htm#wp1179839

Search for its patch and fix registry related issues using Reginout.

have a look at the cooling fan whilst it is running, it may have seized up from dust or dirt

There is not a reset button that model. The only other way to force restart it would be to unplug the computer from the outlet. This is not a recommended method but, it can be used a last resort if your computer is hanging.

Disable the turbo memroy driver and see if it will let you go onlin, if so download the driver or updated driver (if any), then unistall and reinstall it. If it won't allow you to do this, then try a system repair with your recovery or operating system disc.

http://direct2dell.com/one2one/archive/2007/04/09/10675.aspx

This is a known factory defect. Dell has a recall on it for Inspiron 9300 shipped between Nov 2004 and Nov 2006.

I just called Dell Tech Support (1-800-624-9896) to get this replaced and they are fixing it free of charge because I bought mine in December 2005. They are sending me a postage-paid box to ship back the laptop (remove the battery before sending it back to them, per instruction).

NOTE: Not all Tech Support people are well trained. The first time I called earlier today (Nov 21, 2007), the tech said (incorrectly) that only units shipped between Feb and March 06 are covered and denied that Dell would cover it for me. I was fuming mad.

Then I surfed around and found the link above which is Dell's official response. I called Tech Support back and got a better tech person. Moral of the story >> if you're certain your computer is covered per Dell's official statement, don't let the tech guys push you around. Email them the link from their own site if you have to. Better yet, just hang up and call back and hopefully you'll get someone who knows what he's talking about.

When you call Tech Support, have your Express Service code ready. They use this number to loop up whether or not your laptop is in the recall group. This number is at the bottom of your laptop on a long skinny oblong white tag.

Looks like a bad Memory dimm, try replacing it.