The 2577 folder is used to install iGO (and any other program?) on WinCE devices. Of those, there are 2 kinds: PNA (Personal Navigation Assistent) and PDA (Personal Digital Assistent). The latter have developed into smartphones.

One can either copy the folders to a blank SD, put it in the device and start the device. If the device is capable of handling this method (all PDA on WinCE are), it will install iGO. I know, I had a few PDA (HP iPaq, Mio, ...)
PNA won't install iGO that way.
The other way of installing is to rename the application.dat, as DII pointed out.

And there some 8.3.2 builds that are so called official PDA builds: like 8.3.2.152657 and 8.3.2.138649. I am even sure there are more. And I think (not sure) a 8.3.4 for PDA exists.
A remark, most cracked builds (or all?) are capable to run on PNA and PDA, as the list of Maury22 shows, but PDA capable is not exactly the same as an official PDA build.