Tides of Avarice and update 5.00 recently released, but I cannot update my current version which is 4.2.
There should be a 4.2 to 5.00 patch for the offline files shouldn't there be?
I still have Windows 7 so I can't use GOG Galaxy.

Presumably removed due to being too many versions behind. If your internet connection really is terrible, you can try asking GOG support nicely for it and then expect to wait so long that several new versions of the game will have arrived before you will get a link.

Yeah, don't bother with support. All they will tell you, in the end, is "nope, sorry". I've asked this question for several games and (aside from one time they told me to contact the developer) that's all I ever got out of 'em.

It sucks, but you'll have to download the installer all over again :(

And a couple of new versions of the game are out since the beginning of this thread, namely 5.10 and 5.10HF1.