PC slow and lags,then automatically shuts down in Windows.

[Vildano]

First,I had a problem with laging and freezing,then crashing with BSOD.When I asked a neigbhour (he knows a lot about PC's) ,he said to try reformating my PC first.That's what have I done.The problem continued.However,6 days later,it looked like the problem was fixed.But i realized,my PC was slow.Like when i was sliding down pages on Facebook,my mouse was faster than the slide bar,and the sliding down lagged too. When i open up a photo,It was first black,the comment section is blank.After two or three seconds,the picture appeared but the comment section was blank.After one or two seconds the comments appeared.Simmilar experience on Youtube.But something was weird:The videos weren't lagging.However,the page was.When i want to select the pause button,this happens:I move the cursor to the pause button,the pause button remains unselected.After 2 seconds,it gets selected.The same experience when wanting to go to fullscreen:I move the cursor to the fullscreen button,the button remains unselected.After 2 seconds,it gets selected.But the Fullscreen doesn't really go like a charm.When i click the fullscreen button,the video remains in its original size and it's on its original place,but around it is some dark gray colour around it.Then after 2 seconds it gets in the top left corner,remaining in its original size,still some dark gray colour around it.The video lagged.
But i didn't care.I downloaded Sonic Adventure 2,to test can my PC run atleast low spec games(before that i checked on http://www.systemrequirementslab.com/cyri can i run it).The game was laggy,but no freezing or crashing.But then at one point my PC just shut down. My PC case is open on one side,and whenever it crashed,the CPU and GPU was very hot.Some people told me to run CPU Thermometer.And,I did.When the computer isn't doing anyithing it says that the value is 2.8%.When the computer isn't doing anything but being on a page,the value is around 0.0% to 10%. When i am loading a page the value rises to 100% +
Since i started playing Sonic Adventures 2,the PC now shuts down on random big tasks(Like being on multiple tabs on Google Chrome,watching long youtube videos,and while playing other video games,even the ones on Facebook) So please help me!

My PC specs:
Operating System:Microsoft Windows XP Professional (5.1, Build 2600)
Language:English
System Manufacturer: GBT__
System Model: AWRDACPI
BIOS: Award Modular Bios v6.00PG
Processor: Intel(R) Pentium (R) 4 CPU 3.00ghz (2CPUs)
Memory:1024MB Ram
Page File:694MB used,1764MB avaible
DirectX Version: DirectX 9.0c (4.09.0000.0904)

Display:
Device:Ati Radeon X1050
Approx. Total Memory:512.0 MB
Current Display Mode: 1280 x 960 (32 bit) (75Hz)
Monitor: Plug and Play Monitor

Please help me this problem is driving me crazy.

 

[hang-the-9]

Sounds like a heat issue, but may also be a power supply or motherboard issue, especially due to the age of the computer. Check the motherboard for any puffy or leaking capacitors.

With an P4 system with only 1 gig of RAM, you can get 4 times the speed for $80-100 by getting a used Core 2 Duo system in the 2.4 gig + range, you will probably get 2 gig of RAM and a larger hard drive in the process. Since you did a lean setup of Windows and the issue did not go away, it's a hardware issue which is not worth at all spending money on to fix in your case.

 

[Vildano]

I am actually buying a new computer for a couple of days but my friend is about to go on vacation,and he wanted to play Minecraft with me before he goes.So i tought a solution without spending money would be perfect. (Actually,Minecraft on low settings doesn't lag much,but the PC shuts down)

 

[Black_Plague]

It might be a failing hard drive. I know it sounds weird. But it really can be a failing disk. If you did carry it around fast or accidentally just hit it to a wall (slow hit counts too) while working. It creates a huge bad sector at disk. And when computer tries reading data it takes more time. Afterseveral read tries the bad sector becomes worse. And which causes pc to stop and shut screen.
How do i know? I had exact same issue and then one day my computer didnt start. I opened it's insides. Everything was fine. Until i got to the least suspicious thing the hard disk. My hard disk was full of small scratches... Too many of them... Too many bad sectors. Anyway my computer was old, so i m going to buy a new one soon LOL.

 

[Vildano]

It could be.I changed my Hard Drive that was completely not working,and now this one is suspicious,because it's not new.It's really old:It's from a pc 14 years ago.We even doubted it will work because it was the time of the still weird looking PC's (Sorry,i really don't know how are they called in English language XD)