Since we have pretty much run the gambit of repairs for the operating system let's look a the possibility of a hardware problem.
Most all hdd manufacturers have a diagnostic tool for their hdds. I would like to run a scan on your hdd, but in order to provide you with a link I need to know who the manufacturer is. To find out who this is you will need to remove the hdd to see the label. This link will take you to a video hdd being removed from a 5738G. One thing I will suggest is to touch something metal close at hand to discharge any static electricity, electrostatic discharges can damage components inside your computer. Once you know who the manufacturer is post it here.
In the interim I would like you to run a scan on your RAM.
1) Please download the Memtest86 Pre-Compiled Bootable ISO file.
2) Unzip the downloaded memtest86
file. You will need a program like 7-Zip
to unzip this file.
3) Inside, you will find the memtest86 file.
5) Insert blank CD into your CD drive.
6) Open ImgBurn, and click on Write image file to disc.
7) Click on the Browse for a file... icon:
8) Locate the memtest86 file, and click on the Open button.
9) Click on the blue arrow to start burning bootable memtest86 CD.
10) Once the CD is created, boot from it, and memtest will automatically start to run.
Please note: It may be neccessary to change the boot order in the BIOS so the CD/DVD-ROM is the first device in the boot order and the hdd second.
Each pass consists of 8 tests, it is suggested that you run at least 7 passes, this will take several hours, you may find it simpler to let it run overnight. The longer you run the passes the more comprehensive the results will be.
If you are running multiple modules and have a failure, remove all but one module and test it separately, continue this with each module till you find the one that failed.
When you discern that a module is good, use it to test each slot to be sure there isn't a problem with one of them.
When the test is complete a display similar to the one below will appear. Note the locations of the Pass and Errors, any Error is indicative of a failed module.