A machine that was manufactured only five years ago should be able to run any Linux distribution fairly well (half a gigabyte of memory and ten gigabytes of disk space should enable a newcomer to Linux to try out pretty much any distribution quite comfortably, assuming that the machine has a CPU speed upwards of one gigahertz --- trying to run Mandriva on a Pentium III, for example, won't be a terribly pleasant experience
). The "best" Linux distribution is a subjective assessment and really would depend upon your requirements --- take a look at DistroWatch (the most popular distributions are described on this page
) and figure out which suits you best.
...As for which is the most up-to-date, many of the major distros have a fairly regular release cycle: for example, Fedora's latest release was just four months ago, at the start of November last year; Ubuntu's latest was the month before, and their next releases are scheduled for the month after next. Between releases, updates are available and the process of downloading and installing them is usually pretty straightforward.
Hope this helps: good luck!