Hardware too old? Perhaps you mean old hardware that is faulty or dying. At my job I have a Suse SLES 9 system that uses kernel 2.6 on a Pentium3-450 and it is fine.

Code:
$ ssh root@SLES9-test-server
Password:
Last login: Mon Oct 17 17:03:20 2005 from chuga.company.com

Welcome to SUSE LINUX Enterprise Server 9 (i586) on SLES9-test-server


SLES9-test-server:~ # uptime
  2:06pm  up 26 days 19:46,  1 user,  load average: 0.09, 0.02, 0.00
SLES9-test-server:~ # uname -a
Linux SLES9-test-server 2.6.5-7.97-default #1 Fri Jul 2 14:21:59 UTC 2004 i686 i686 i386
GNU/Linux
SLES9-test-server:~ # 
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 7
model name      : Pentium III (Katmai)
stepping        : 3
cpu MHz         : 448.998
cache size      : 512 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca cmov pat p
se36 mmx fxsr sse
bogomips        : 886.78

SLES9-test-server:~ # cat /proc/cpuinfo
At home I have used Debian 3.1 sarge & kernel 2.6 on a Pentium II-400 & make the system a DNS & NTP server.

Most crashed systems are related to HW failures. Bad RAM, slowly dying motherboards, corrupt HDs. Its been years since I have seen a complete system crash from a kernel problem.