Just because you have an older computer does not mean you are out of the woods for getting a newer operating system. Here are just three examples of linux and bsd that support older computers. The best part is you can get the cd’s for a nominal cost or less if you know someone who can download and make the cd’s for you. Debian might be the best choice to start with of the ones on this list.
Almost all i386™-compatible processors with a floating point unit are supported. All Intel processors beginning with the 80486 are supported, including the 80486, Pentium, Pentium Pro, Pentium II, Pentium III, Pentium 4, and variants thereof, such as the Xeon and Celeron® processors. All i386-compatible AMD processors are also supported, including the Am486®, Am5x86®, K5, AMD-K6® (and variants), AMD Athlon (including Athlon-MP, Athlon-XP, Athlon-4, and Athlon Thunderbird), and AMD Duron™ processors. The AMD Élan SC520 embedded processor is supported. The Transmeta Crusoe is recognized and supported, as are i386-compatible processors from Cyrix and NexGen.
Slackware Linux can run on 486 systems all the way up to the latest x86 machines (but uses -mcpu=i686 optimization for best performance on i686-class machines like the P3, P4, Duron/Athlon, and the latest multi-core x86 CPUs).
Nearly all x86-based (IA-32) processors still in use in personal computers are supported, including all varieties of Intel’s “Pentium” series. This also includes 32-bit AMD and VIA (former Cyrix) processors, and processors like the Athlon XP and Intel P4 Xeon.
However, Debian GNU/Linux lenny will not run on 386 or earlier processors. Despite the architecture name “i386”, support for actual 80386 processors (and their clones) was dropped with the Sarge (r3.1) release of Debian. (No version of Linux has ever supported the 286 or earlier chips in the series.) All i486 and later processors are still supported.