Is this a client machine with altiris on it that you want to reset the windows password for, or a unmanaged machine? Also which screen can you get upto? bitlocker screen, windows logon a boot login?
if its a managed machine you should be able to create a task with a net user command which would do it (if you have no other security in place).
You can download a windows 7 iso for free on the microsoft website if you want o rest the password in safe mode (theres loads of guides online for that). if none of the above work, your probably posing in the wrong forum.