I am with The Lonestar on this one, check to see if the cooling fan is working. use the laptop on a hard flat surface for better ventilation. Will it cut out quicker if it's on your lap or on soft furniture?.
1. How to calculate power draw per rail, to see if Power Supply can handle the load?
Your fans and CPU cooler will run from 12. All the others will run from various voltages derived from either 3.3 or 5 volts, and without the detailed specs, you cannot tell the current levels at any voltage. However, since your computed max power is 169 watts and the supply is only rated for 160, regardless of how it's divvied up you are probably in trouble. That's not to say it wo not work, necessarily, since it's entirely possible that not all the components will require maximum power and at the same time.But it's probably not a good idea trust this. Murphy's Law applies.
2. Is it possible to change an older computer to a gaming computer?
You would have to replace just about everything in the case, sims 3 is quite demanding on a PC so new motherboard, CPU, RAM, power supply, new graphics card, new hard drive and then you are sorted, the power supply needs changing because all nnew graphics cards that are any good for gaming needs PCI-E power conectors and atleast 24 amps of power on the 12 volt rail so if you grew up with the PC then I take it the PC will have APG graphics and old style PC-3200/DDR400 ram in it hence the ram upgrade and GPU too. Its sad to say but I would just buy a new PC. Sorry to be the bearer of bad news though.
3. Is it worth upgrading my gaming laptop to a gaming PC?
this really all depends tbh i mena ur laptop is still a pretty good gaming laptop and should last u another 2/3 years atleast maybe more depending the games u play b4 its outdated for gaming. if ur after a big screen then just buy a monitor and attach it to ur laptop or attach it to ur tv via hdmi cable. the advantages of a gaming pc is that it can be upgraded as u go along like the cpu,power supply,graphics etc whereas on a laptop u can only upgrade the ram and hdd which is it. therefore gaming pcs generally last longer in the gaming world but like i said urs is seriously powerful and should last atleats 2 years or even more and u can always upgrade ur ram or hdd plus its portable. gaming pcs are usually cheaper then desktop pcs. so have a look on ebay or something and see what other people are selling similer spec laptops then look into how much a gaming pc same spec or better then urs is and decide.
4. Is it a good idea to place the Power Supply Unit Below the Hard disk?
Lots of cases do it these days. The 'traditional' layout with the PSU on top was designed to draw in air and blow it into the processor to help the processor heatsink and fan (as counterintuitive as it seems) - modern systems run cooler, have additional fans, generally, cool the system efficiently enough that the warm PSU air is not really needed.The bottom PSU simply draws in air and blows it out to cool itself.Now, working out why your drives are failing is not that hard. You are already looking at the SMART information on the drive I hope - check what the maximum heat on them is - overheating can cause problems. Look at the age of the drives and age related variables. And well.. drives fail.I would guess overall its probably not the PSU.
5. DISK BOOT FAILURE after upgrading power supply
My PC also refused to boot without the installation disk in place, after a re-install of Windows 7 that renamed my old Windows folder to "windows.old".I was about to go for the Repair operation but decided to check the BIOS (for boot priority) first and discovered that the reinstall had somehow disabled my HDD in the BIOS. Because of this, the BIOS was saying that there was no drive present on the PC (this would be enabled once the install disk started to boot). Anyway, I enabled my HDD and the problem was solved