What version of Windows are you using?
What has changed? You said you downloaded HM pro after the free trial expired, did you install it or just download it?
Please explain exactly what you see when you power up.
Write every message you see in order until it stops booting.
Does it give you the option to press F8 to boot into safe mode?
Once we know what you’re seeing and what O/S you have and what exactly has changed, we should be able to help although it might require reinstalling Windows and it sounds like you don’t have the disks. You might have an emergency partition Toshiba put on there with the O/S on it and you might be able to recover that way as well.
vista home premium service pack 2
yes.downloaded hitman pro paid version and rebooted after scanning.
f8 is not an option.