Fresh Windows 7 Install Freezes

I purchased it from microsoftstore.com

Something must be really ****ed up. Windows 7 CD won`t boot, and spitting out a Code 5 error. All working fixes somehow includes having a earlier/older version of Windows installed. I`ve tried loading MS-DOS with CD-rom drivers and then running setup located on the Windows 7 CD, but MS-DOS only recognize README, and nothing else. Weird?... Yeah! Now Windows VISTA can`t be installed either. Which leaves me with... No OS

Confirm the HASH on your MS ISO download against the official HASH.
HashTab... is the coolest thing ever!
Windows 7 RTM SHA-1 hash - checksums
If your download includes SP1 just download another or get HASH from Technet Downloads "Details" tab here: http://technet.microsoft.com/en-us/s...s/default.aspx.

Then burn confirmed ISO to DVD using ImgBurn at 4x speed with verify. Make sure it says bootable in text at left when ISO is loaded.

See if you need a BIOS update. If not, reset the CMOS: Clear CMOS - 3 Ways to Clear the CMOS - Reset BIOS

While in BIOS setup, set SATA controller to AHCI mode to try install.

Do you have another computer you can move the HD to try install with only it plugged in, then after install SysPrep the HD to remove all drivers to move it back to problem computer? SysPrep to move HD to another computer

Unplug all other HD's and peripherals. Use PS2 mouse and keyboard.

Hm, I somehow got Vista installed - after much back and forth. The issue stil remains, but now happen more randomly. Yesterday I used the computer throughout the day, and it froze somewhere between 5-10 times. Before it happen right after login.

I still want to try to fix this of course, quite annoying when this happens. How can I check if I`m in need of a BiOS update?

CMOS has been reset.

Work through these troubleshooting steps

I'd stress test the RAM overnight with memtest86. Reseat the RAM, checking the slot for any dust or debris to blow out. YouTube - Reseating your RAM, Video Card, and Hard Drive

Which HD diagnostics extended scan did you run? Run Disk Check

Run Prime95 to test your System more globally: http://www.mersenne.org/freesoft/

Gregrocker: You definietly, but not alone, deserve a big thanks for taking your precious time to help me. I really appreciate it.

I ran remtest overnight a few days ago, with no bad results. HDD scan was fine too.

Maybe I`ve said this before, and maybe it`s no usefull information, but;

the PC is somewhere between 2-3 years old and owed by a old lady, who has never physically touched the inside of the computer(removing, adding hardware) and nor does she know that things like BiOS exist. And the PC has worked flawlessy for those years, up in til now.

Check the temps with SpeedFan, compare to the CPU's maximum temps via Google.

Once you open the case, it may need to be thoroughly blown out with a can of air to get rid of the dust in the fans, CPU, Power Supply, etc. This is easy but requires care not to touch the electronics or spin the fans too much:

had vista on a old acer 5050 upgraded to windows 7 before this deleted all old partitions etc.
Installed windows 7 and it kept freezing on startup. Tried to reinstall 2 more times with different discs. Eventually I let it try safe mode but told me that couldnt start in safe mode for the 1st time running. But low and behold just after trying safemode it worked, somehow safemode changed something#