Bill wants to be automatically reminded when to defrag his hard drive, remove junk, and do other chores.
There are plenty of options here. For one thing, many such maintenance programs have their own built-in schedulers. Using these may not be the best solution, however. You don't want to constantly run five separate programs so you can be reminded to do five separate chores.
Windows' own Task Scheduler makes more sense, especially if you're running Vista or Windows 7. Click Start, type task, then open the Task Scheduler option. Click Create Basic Task in the right column and follow the prompts. You can set up a task that will, at the scheduled time, start a program, send an email, or display a message. That should pretty much cover your reminder needs.
XP's scheduler isn't quite so convenient. For one thing, it can't display a message or send email--only launch a program. Of course, there are ways to make this effective. You could schedule it to launch your defragger, or to load Notepad with a particular text file ("Take out the trash").
Another problem with XP's scheduler: It requires you to have a logon password, which the scheduler has to know. For more on that issue, see Schedule Tasks in XP.
If you still want to use XP's Task Scheduler, select Start, All Programs, Accessories, System Tools, Scheduled Tasks. Double-click Add Scheduled Task and follow the prompts.