I have a BIG thing called Sidekick98 (scroll down) that does maybe more than you want...complete calendar, to do lists, address book, time zone mapper..etc...
if that's too much, there is a little 'sticky' program called ...well,,, "Stickies" which gives you little hide-or-show notes with settable alarms...

(I have and use BOTH of these daily, and they are both free)

If those don't work, there are several other PIMs (Personal Information Managers) that I have seen that are like smaller versions of Sidekick, and several other 'Sticky Note' programs. Let me know if you'd like more choices..