Q: How can I download a trial version of Linux 5 for free?

A: You can download any number of distributions, but unless you got a ISDN or T1 connection, it will take a long time. I generally recommend getting a CD-ROM from

http://www.cheaplinux.net/
http://www.cheapbytes.com/ ,
or
http://www.linuxcentral.com/ .

It's cheap and less painful. By "Linux 5", I assume you mean Red Hat 5.0. Red Hat has all its software packages and boot disks on its site, but putting them together might be a little hard. If it's RH 5.0 you want, then a few bucks on a CD-ROM is easy trade for your time and effort.