itunes 10 installs but says unknown publisher invalid digital signature

I see you're from Australia, belinda ... by any chance, are you connecting to the internet via a wireless broadband provider, using one of those USB dongle thingies?

i'm using a broadband internet modem and its connected to a wireless router

Okay, that rules out one possible cause of the installers getting damaged during the download. Starting to check through other ways past this for you.

What web browser have you been using to download the installer? Does it make any difference if you use Firefox instead of IE, or vice versa?

Yes, definitely worth a try ... Firefox handles network connections a bit differently from IE and most other browsers. So if IE is downloading the installers damaged, quite often Firefox can download a working one. (Every now and then it works round the other way ... Firefox is grumpy, but IE or another browser gets the business done.)

Should I just get the itunes setup folder from a person that has got it already?

Yes, that usually works. (So long as we can get an undamaged installer onto the PC with one of these, it will usually install fine.)

Another thing that is worth a try is seeing if you can connect to a different wireless network, and downloading the installer while you're connected to the internet that way. (The wireless router being grumpy is a common cause of this sort of thing, so by connecting to a different network you're taking the grumpy router out of the equation.)

🙂 excellent news, bel. Glad you're up and running again.