Virtual Server/PC Tip: clock=pit Deprecated
If you use Microsoft Virtual PC or Virtual Server and have Red Hat, Fedora, or CentOS Linux guest OSes, you probably have clock problems. Clocks basically lose an alarming amount of time may be hours off within a day or two. You may also have repeating keys problems when typing. Microsoft's Ben Armstrong (Virtual PC Guy) posted a tip a while back...
Repeating keys under Fedora and Red Hat Enterprise Linux
...that pointed to a Microsoft Knowledge Base (KB) article that recommends adding the clock=pit (programmable interruptible timer) option on the grub kernel line in /boot/grub/menu.lst. However, if you started using RHEL 5 (CentOS 5 in my case), take a look at your /var/log/messages file. You will probably find a warning that the clock= option has been deprecated. From what I can see, replacing it with...
clocksource=pit
...takes care of that warning. However, the RHEL 5 based Linux clock still runs a bit slowly. I ended up having the clock sync with a time source every hour to deal with it.