Khadgar42: It's an Lenovo Ideapad Y510,
and I've tried to switch the booting order in the BIOS without success.
[edit]
Wait a minute...
there is this button next to the power plug.
Oohkay, so now I can restore factory settings but I will lose my data. Mphh... No repair mode, sadly
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Contact support and ask for a recovery disk(s).
Got a 530W Thinkpad last year, created the recovery backup on a bad medium and it wouldn't let me create another recovery medium.
I contacted support and they shipped me a bunch of recovery disks without charges (mind you, it was for a premium laptop and the warranty wasn't expired).
My gf's old laptop was an aging HP, the warranty was expired and she had no recovery disk. I contacted support and they sent me the recovery disks for like 30$.
Usually, companies are pretty cool about sending you recovery disks for their laptops and won't charge you an arm and a leg for it. It's just good support and an essential strategy for repeat business.
PS: If you need to recover files before formating, they're a way to start Windows on the command prompt if you finickle a bit at boot time.
From there, you can copy/paste your files on a recovery medium (ex: USB stick) and if you really suck at the command prompt (and can't be bothered to google it), you can open up notepad (just type "notepad") and use notepad's open/save menu to copy your files (yeah, Windows is way too permissive with what it lets you do with its open/save menu).