want to reinstall windows, but lost windows 7 64bit disc

my computer use to have windows vista until l bought a windows 7 64bit last year and installed windows 7 64bit. l want to reinstall it, but lost the disc. Can l contact microsoft for a replacement disc or replacement?

Highly unlikely. You will need to find the disk or buy another. But if you still have Windows 7 installed, you can find the key, in your OS, that you have used, download another copy of the OS from a reliable source, and reinstall using your present legit key.

davehc, thanks for reply,
l noted down a while ago:

"PRODUCT KEY:
BB4BM-VH7GG-GTR8D-XXXXX-XXXXX
proof of licence / certificate of authenticity:
X15-XXXXX"

but can l find the details in my OS, if so how? and do l just go to microsoft.com to download windows 7 home premium 64bit and then put it on a USB stick / burn onto dvd? could you give me the exact URL to download this?

thanks again

Do you still have your product key? If so then you can download the ISO image of the DVD install at Official Windows 7 SP1 ISO Image Downloads

You can also download SIW or AIDA (formerly Everest) to find what your product key is on your computer.