Old versions are crappy versions. Almost month by month linux is getting better and easier to use, unfortunately Distros like Redhat use full-fledged desktop enviroments that require the extra power that todays computers can put out.
Not all of them are like that though, give Slackware linux a try. It's a bit harder to set up, mainly in the X windows department, but it's up to date. Avoid using full fledged desktops like kde or gnome (you can install them if that makes it easier, just don't use them), use something like fluxbox or IceWM. Then you will still have pretty good speed.
If you don't like Slackware, or Debian try using SuSE, I don't know what the minimal requirements are for it, but otherwise it's much like Redhat. Otherwise You can gotto Linuxiso.org and they have some 7.X iso's aviable.