This laptop was new 08/2013 and came with Windows 7. This was upgraded on release to w8 then 8.1. A month ago, it started to hang on bootup - from switch on, it clicked once, displayed 'Press ESC for boot options' and halted. Occasionally when it did boot, diskcheck started but found no faults.
Eventually, it failed to boot so often, I took it to the HP Care Centre in London and explained the problem. Three days later, it was 'ready for collection' having been set to original format (W7) and I was told no faults were discovered. It worked for two days so I upograded to W8 but attempts to install 8.1 always failed near the end with 'unable to install' message.
Now, old problem with boot hanging is back and the rate of failure is about three times in five.
I am loathe to take it back to HP if someone has any good ideas to try first.