It honestly depends on the load the PSU is being forced upon. If your system load is too much for the power supply during operation, your system will probably power down or reboot. If it's too insufficient for powering the system up, it won't start up at all.
quoted the wrong post
Would the PSU overheat, forcing it to power down?
Because when i play demanding games, my computer overheats and powers down, PSU being the hottest component.
Very short story of the douchebag who had to reinstall vista due to DRM:
Vista was causing huge problems and computer was overheating at desktop *cough securom cough* and constantly BSODs.
Reinstalling vista using the stuffty Dell DVD fixed it, but then i realized, it's a loving barebone vista install.
There was no drivers, period.
Couldn't download drivers for the computer because I couldn't find the model and to my luck, i found a driver DVD.
Installed that motherforgeter and what do i get?
Oh, just a menu that has a hidden extract button, wanna know why?
Oh, the computer was running at 800x600 and there was no scroller, Dell definitely tried on that one. /sarcasm
So, I plugged in a SD card into my laptop and started downloading NVIDIA drivers and plugged the SD card into the desktop, to my unsurprise it didn't work.
USB POWER GO!
Plugged in the camera and used it like a USB flash drive.
Installed NVIDIA drivers and maxed out resolution (1440xsomething, i assume 800) and installed the drivers, network and everything regained.
End story.
Installed some games and it overheated on the medium-high end games. Blockland worked fine apparently.
stuff.
If a new PSU doesn't work, then all this computer would be good for is an outrageously fast DVD burner, no errors either.
Notes for the story:
People say vista takes 2 hours to install, yet i installed it in 30 minutes on a somewhat weak computer (AMD Athlon (not athlon II) x2 at something Ghz)
I have a NVIDIA 9800GT paired with a 350 watt PSU.
Before reinstallation, computer took like 40-50 bar passes to start up. (1-2 minutes to start up)
Now it only takes 2-3 passes. (4-5 if updating, which is less then 10 seconds and around 10-15 seconds on update startup)
I think I should go to Newegg and purchase a new PSU, maybe a 450 watt since I wont be upgrading this stuffputer.