No worries then

I was going to suggest something very simple that I do and that is just use notepad.
If you create a folder and then just put loads of text files in there with the info of all your customers (each on a separate file) then you can search everything just using the normal windows search. You type in Sussex and it'll return all the .txt files that contain Sussex in the content. Dead easy and simple to back up
I guess if you want something more complicated like ordering your customers according to how much they have spent then you're probably better to do it in a spreadsheet
James.