How to make sure I can restore the OS which came preinstalled on my laptop?

I'm fond of using System Rescue CD to take a complete (bit-wise) image of the drive. I usually use an external USB drive and I use dd to make the image. This isn't fast, and it requires the external drive be larger than the internal, AND that the external be formatted with something that can take large files, but it's reliable - you don't have to worry about some idiotic recovery utility building the files wrong, or something being unable to activate or whatever - turn the new machine on, get your OS activated (for Windows systems) and then shut it down and take an image.

You'll never have to worry about what to do if the HD eats itself, you can ALWAYS fall back to original install.

you can take matters into your own own hands and backup your IdeaPad with EASEUS ToDo Backup.

It also works with BartPE via USB stick (WinToFlash) so you don't need a DVD drive to boot from.

Here's a tutorial.

All programs mentioned are freeware.

You should also keep a backup of your Windows 7 Activation files:

How to Backup and Restore Windows 7 Activation Status (Activate Offline On Reinstall)

It happened to me that I couldn't restore from DVDs that where created form the vendor provided "Rescue DVD Creator Program".

Thus I would recommend that you use something like Acronis Home, see: http://www.acronis.com

... and: yes, Leonovo should have enclosed a restore DVD. But unfortunately the lack of a such a 50 cent DVD seems to be common practice by all the vendors I know ...