PC issues unsure whats wrong

[XxiI_ARES_IixX]

Computer started to become sluggish, I was playing Minecraft, then all of a sudden got a blue screen and it shut off. I tried turning it back on and from the Windows load screen it would instantly blue screen and restart giving me a boot disk error, I decided to come to terms with my loss and reinstall windows, however the install wouldn't show my HDD, I messed with it for a while, plugging in a small external hard drive, it read that, but won't read the internal hard drive. keeps asking me to load drivers but won't give me the option to format the partition because its not reading the hard drive, I checked bios and it reads the hard drive, but not the windows install. This is the second time this has happened, I got it to install windows after messing around with it, for some reason it recognized the HDD after I plugged the external hard drive into the USB, however it was really slow, and had trouble running programs, after a week it stopped working again, giving the quick blue screen and restart, there's no way of seeing what the bsod error is showing because it is an instant restart. I don't want to waste money on getting a new HDD or RAM if its something more serious.

 

[Benevolence]

This could very likely be a hard drive failure.
EDIT (have better ideas)
Open command prompt and run: sfc /scannow
This will check the operating system for file corruption, and attempt to fix any errors.
Next you will need to enable error checking of the disk. Go to My Computer, right click on the disk > Properties >Tools(Tab)> Error Checking > Check both boxes (Auto Fix, Scan for Bad Sectors)
Reboot the system and allow time (could be hours) for the system to check the disk. If there are errors which can not be repaired, consider buying a new drive.

If everything checks out OK, make a bootable CD or USB drive of Memtest to check the RAM. Memtest.org
It could also be the power SATA/IDE cables connected to the drive, try switching the out to rule out cable damage.

 

[D_Know_WD]

Hi there XxiI_ARES_IixX,

In case you have some important data on the HDD, I would advise you to back it up until you resolve the issue.
If your system can still boot, it may be a good idea to download a brand specific testing tool and test the HDD. The results will eventually show you the HDD's health status. It will not hurt to change SATA and power cables as well as the SATA port.
If the HDD passes the test and changing cables and ports doesn't help, you should start troubleshooting the other components. Checking the RAM for example, as Benevolence already suggested.

Hope this will help,
D_Know_WD