Restoring laptop to factory default?

[The_One]

My acer aspire came shipped a few years ago with windows vista on it.

It now runs windows 7 premium 64bit.

How do i reformat the hdd with a fresh windows vista on it as i have no disc

 

[The_One]

Deleted all the acer stuff yonks ago and i cant download acer emanagement it wont let me install it due to windows 7 being installed.

Im currently acquiring a windows vista installation disk then i presume i can use the code off the bottom of laptop to install it?