First of all, it's quite easy to check how Windows was installed: If UEFI you'll find an EFI partition; otherwise you'll find a small (~100MB) partition at the beginning of the drive.
Regarding how to boot the installation media, if you have the UEFI+Legacy setting in UEFI/BIOS youĺl have two entries in the one time boot menu for all bootable device, one with UEFI being explicitly mentioned and the other without it. Typically:
Code:
UEFI: Generic USB storage (UEFI mode)
Generic USB storage (Legacy)
If you have some new (or relatively new) nvidia card/chip you may need to boot with the nomodeset parameter.