How I connect a 20 year old machine that has a RS232 port to my computer?

I have a problem.. i have this thermometer that in 1990 was a hit.. it has a data logger and my problem is that I need to have a connection with a computer to download all the data.. I've tried with RS232 controllers but it doesn't work.. I don't have the software because is out of date and in the manual said that is MS-DOS based.. Suggestions? Please!