Some test with Windows 8.1 Update 1, using Windows 7, 8, 8.1 Yesterday I got the macine from an friend which wasn't start Windows 8.1 Update 1 anymore. It stand either at the W8 Logo, gone to the Repair Process, just rebooted or even din't started at all. So, what could be the problem: Hard Disk 500GB SATA3, 3 years old going to be die? CPU problems because of over clocking? Memory Problems? Mainboard? Old BIOS? or anything else? Seems to be that the CPU was working OK, over clocked but good cooled with an working temp of below 55C and even set the clock to normal same problems happen. BIOS? OK, I updated to the latest BIOS, still the same! Memory? Tested in an other machine: worked just well! OK, HDD! Took an new 1TB WD Green HDD and installed Windows 8.1 Update 1 and got problems whithin installing! Install wasn't able to finish. So, took Windows 8.1: same! One step more back to Windows 8: Installation finished, done some updates, installed a few apps and the problem started again, sometimes but every time! OK, back to Windows 7 and all went just well! But that wasn't the solution I was looking for. Before I do any work on an machine, I clean that machine from dust using an Airblower. So, what prevent that machine from running Windows 8 to 8.1 Update1? In my last step, I was again take out the memory modules and used an soft pencil rubber for to clean the feet, also used 96% pure alcohol and an clean toothbrush for to clean the memory module sockets from remaining dust inside and viola: ALL worked well with the original installed Windows 8.1 Update 1 on the old HDD! Resume: For me that clearly shows that from Windows 8 onward, the OS is much more sensitiv about the used components, here the Memory Modules, than older Versions. To keep the computer clean as best as possible, would be essential for to have an system running well That will also result in an order to the staff of my company for to shorten the cleaning cycle of customers computers from 3 month to 45 days starting immediately. Till now with the 3 month we didn't had such problems within our customers,but who knows?! So shorten that cycle would for sure be efficient in the long run! Thinking that this experience may would help some members of MDL in the future too, I created this new Topic. Have a nice day.