Great suggestions! Thank you everyone

Instead of totem-posting, I'll just do one post here to respond...
@Treasure - Thank you for pointing me to someone who does something similar. Is the shop name "Gerri's?" (Haven't been online this morning yet.) I recall Mickey saying she sent a note to customers, but I *think* she kept track like I'm currently doing; however, jogging my mind re: Mickey gives me another person to ask. Thank you so much.
@Suzanne - I'm almost ashamed to ask this as I taught beginning DOS for 12 years. That was prior to Windows, though. I have used DOS since Windows on occasion to troubleshoot problems, but can I stay in Windows to use the DOS sort command with notepad? If so, how would I do that, please? If not, how do I get my list in DOS to sort?
@Ava - Windows and free options. I don't want a heavy database program for sure. I have Excel but just looking at that spreadsheet makes my head whirl. OpenOffice, especially the kids version, may just be the answer!! I've heard it recommended on computer shows as a great, free alternative to the comparable Windows group of programs. Thank you, Ava for the URL; will be heading over there!

@Ciaran - /me runs screaming hearing the dreaded "E" word again.

(I wish Excel *was* something I could work with easily, but I have some kind of "block" against that program. I think it looks to "accounting-ish" and being an English Lit. major it truly makes my head hurt.)
@Melita - There are definitely a lot of great uses for a database program. I know in the past when I would look for a certain type of program or app. in tucows.com I ran into some really easy-looking database programs. Of course that's when I didn't need one.

I may head back there and do a more thorough search. Come to think of it, I may have looked at cnet.com instead prior to posting this to ask for ideas. The most basic, and what I am looking for, is one that just pulls *whatever* (in my case names) from an alphabetic list. But I love the cross-referencing features such as "Who purchased xyz product from me."
I keep note card lists within SL for various categories (ie. Dancing, then sub-cards for types (ballroom, jazz, 50's, etc.). When I'm on the forums, I'm not in SL generally, so it would also be great to use a database for that type of info so when someone asks, "Where is a good place for..." I would have it handy on my desktop instead of having to open SL.
@Ann - Does wingrep work on Windows as well? That sounds like a cool program...and I have alllll my logs since the day I began SL.
@Amar - LOL...I had to grin at your not wanting to creep people out. Basically the same reason I want to keep track of who I have already thanked - I want to thank someone the first time they purchase from Czari's Attic, but not keep thanking them with the same message if they purchase again so it doesn't sound "canned." Right now my alphabetized Wordpad list works, but over time I can see that becoming a bit unwieldy.
I'm really having fun doing it and I will be interested to see if it has a positive affect on my business sales.
Besides...I'm the person who LOVES to sort inventory.

Thank you all again so much for those great suggestions. I am going to try them out and look forward to streamlining this process.