There are two options here as I see it.
You can try to repair the machine to where it was before. If you can find a Windows installation disk, this could be very easy, but it will make Ubuntu unbootable. Given you have data in windows and no data in Ubuntu, this is acceptable. At some later date, armed with more information you can try to reinstall Ubuntu.
You can try to repair the machine so that dual boot works correctly. This is harder, especially for a novice, and the outcome is less predictable. Nevertheless it may be worth trying, especially if experts reply to your question and are willing to help -- you can also try posting on the Ubuntu's own forums, where you may be more likely to get a response.
If you have, or can borrow, a windows 7 installation disk for your Windows 7 flavour (32 or 64 bit), this should give you the "repair" option to restore the Windows master boot record (MBR). See, e.g., http://www.tomshardware.com/news/win7-windows-7-mbr,10036.html. The "repair" option worked for me when I was unable to boot Windows 7 after installing ubuntu 12.04 a year or so ago on a new laptop, but the article I linked to goes into other things you can try if repair doesn't work.
Your problem may be related to issues installing on newer computers which have UEFI mode booting. Normally to boot from a CD you have to change your bios, but with UEFI systems there are two options and you need to choose the right one (see this answer). A good web page discussing how to deal with the resulting problems is https://help.ubuntu.com/community/UEFI. In particular you could try the boot repair tool. There is also a link here to posting on ubuntu's own forums, which I would encourage you to try if you decide to take option 2 (or indeed if you take option 1 and then decide to try installing ubuntu again).
Personally I would tend to favour taking option 1, if you can, or if you are desparate to get your Windows system back. One reason for this is that it may be a lot easier to reinstall ubuntu once you have restored windows (with appropriate advice from here or from ubuntu's own forums). My experience was that the boot repair tool didn't work, and I've seen some comments to the effect that trying to repair an ubuntu system where you installed it wrongly in the first place can be risky.
(A further option you could consider if you repaired using option 1 is to install ubuntu on a virtual machine within Windows. Search the web for this. Using a virtual machine of course may not go perfectly but it's safe as houses, because it's a windows program/data that you can simply delete if it goes wrong. If it does go well it may be what you need.)