How Do i figure out how many bits my operating system is without actually being able to access the desktop?

ok.. so an improper shutdown caused my windows ts stop working so i cant access my desktop...I have a system mechanic disk that can repair windows but it says do not use if you do not know or are unsure of how many bits your operating system is...since i cant access my desktop I cant view my bits. Is there any other way of finding out how many bits my os is (I own a compaq presario f700 running vista home premium)