If you took your computer to a tech shop to have windows re-installed, they undoubtedly simply have overwritten everything and your Ubuntu is gone so the question is, did you re-install Ubuntu after this event and now have this problem. If you don't have a windows installation DVD, it would be a very good idea to create a Recovery disk if you do have a recovery partition with your new install.
Newer systems with UEFI have different install options. I'm not sure what point you are at, whether you have re-installed Ubuntu or not but, the link below is the official Ubuntu documentation on dual-booting with a windows UEFI system.
https://help.ubuntu.com/community/UEFI
It isn't clear from your posts what you can do, boot just windows and not Ubuntu? Neither?
You need to boot the install DVD UEFI (explained at the link) and install UEFI if windows is UEFI or you will have problems booting both systems. This is explained in detail at the Ubuntu link above.
You should be able to verify that you have a UEFI install by running the Ubuntu DVD and opening a terminal and running: sudo gparted
That will show attached drives and partitions and one of them should be EFI.