Hi Hans,

Actually, you don't need a UV source on-board. You could use EEPROM (Electrically Erasable Prigrammable Read Only Memory), or its direct descendant, FLASH memory. Of course, I agree with you and Steve. It would likely be a whole lot easier to upgrade to a more current chip than to set about reinventing all of those wheels.

Paul, I seriously recommend that you check out that Atmel web site and look up their application notes. They've already done the work to do ISP remotely and have published the "How To" instructions right there for downloading. It will almost certainly be a lot less work, and a lot less if-fy, to upgrade your µ-controller (Unless, of course, you have an intransigent boss).