damn. no idea mate. hopefully JMich or someone else more in the know than I will be able to assist.

Usually laptop offers a recovery service on boot, without disk. Are there any option to due this before Win starts up?

What brand/model laptop is it?

EDIT: But like Punished_Snake mentioned above, there's usually a method for entering system recovery from the other partition and hopefully repair/rebuild your boot configuration data. Different brands have different methods for doing this.

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
[/edit]

There usually is FX key which brings a "reinstall" menu. I would sugest to boot up any Linux Live-CD and check with gParted if you have that partition or erased it inadvertly.

If you do have it you can search google/your manuals to search the key or trial and error it. If you have neither DVD's or the partition, you will have to install "manually".

Laptops come with a Windows sticker and your original serial number, so you will still have an original copy. Keep in mind that these have an activation limit though.

But I would say that you have the partition and shall be able to recover your system.

As far as I know you can't fix this issue without a recovery disk but you don't need to buy one. It can be created from any PC with Windows 8 installed on it so if you have a friend that has Windows 8 as well you can just get it from there. Following links have instructions on how to create a recovery disk in Windows 8.

windows.microsoft.com/en-us/windows-8/create-usb-recovery-drive

pcsupport.about.com/od/repair-recovery/a/recovery-drive-windows-8.htm

Consider plugging the harddrive into a different computer to copy your data before restoring. Youtube can tell you how to get the hdd out (I expect that to ruin the warranty, at least my s205 has those stickers absurdly early).

Before you do this, you might give BCDEdit a try:
https://neosmart.net/wiki/recovering-windows-bootloader/

I have to add, though I have used BCDEdit before, that was with a working system so I have never tried the process as described.

The BCD file is the boot configuration data file, so without it you can't start the windows.
Try to do a refresh. Look here for details
It's like a repair install of windows but you get to keep your files.

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).

It does not help you right now but might help others. Now that PC makers save a few cents by not including a recovery disk, they normally have the option to make one. So if your PC or laptop did not come with one, looks in the start menu (or whatever it is in windows 8) for the option to make one. You'll need a CD or DVD burner but I think it is standard on all PC and Laptops now.

Yeah, and f***ing make use you use a quality medium for your backup recovery, like a high end DVD or a newish USB stick.

I used some cheap DVDs for mine thinking I could make as many recovery disks as I liked, screwed it up and then it wouldn't let me make a second recovery medium (told me I was only entitled to one) so I had to contact Lenovo to get recovery DVDs shipped to my place.

Good ideas, so far... Thank you all, I'm working on it...

I wonder how much time I should invest to get it back to work when I can reset everything with a button... Hmmm, have no idea what Data I'm going to miss...

My Alpha Centauri Save Game Files will be sorely missed...

True, but then to start fresh, run updates, reinstall your programs, adjust settings to the way you like it...can take a better part of a day depending what you've lost.