So, I hoped my computer will be back today..

[Hyena]

And it indeed is. But I am not entirely happy about it. So, after an UTTER mechanical destruction of it's hard drive (don't ask), I had broken parts replaced and Windows reinstalled, which is great.
What is not great, though, is sudden blue screen of death that I've got an hour ago. That was NOT a good sign, but the black screen with words "Missing operating system" was worse. I reloaded - still missing. So, I've gone desperate.
I disconnected my optical mouse and external hard drive, freeing both USB-ports and hoping it will magically fix the whole thing. It did. The laptop is now working perfectly fine, but I am too scared to breathe in the wrong direction.
Does ANYONE have any idea about what happened?

P.S.: Oh, the crash happened exactly after I filled both USB-ports.

[An Enemy Spy]

At first I read this as I hoped my computer would be BLACK today. Kind of a weird statement.

[Grinner]

Not sure about the BSoD.

The "missing operating system" message could be the result of your boot order. Have you checked the boot order in the BIOS? Specifically, check that your hard drive is listed before your USB drive; it may have been trying to boot from your external HDD.

[Hyena]

The problem was indeed the booting order, while the BSOD was not seen since then. Thank you.

[Grinner]

You're quite welcome.