If your computer hangs during bootup for a minute or two while loading sendmail, the easiest fix is to just turn off sendmail. Most people don't need it. It's a mail transfer agent / mail server. Most peoples' home computers aren't acting as mail servers, so sendmail is unnecessary.
For Red Hat/Fedora users, to see how to disable sendmail, see the section on ntsysv.
For Slackware users:
$ chmod 600 /etc/rc.d/rc.sendmail
or comment out the relevant lines in /etc/rc.d/rc.M.