1) there's no advantage in using 64-bit Windows in a 4GB system - you'll probably end up with less free memory in the long run
I'd gain roughly 1GB, because the system could map all the hardware resources to a region above my installed memory. I might loose a few megabytes, too, but as a result, I would have more.
2) The error you're getting almost certainly doesn't relate to the amount of RAM, but to the amount of Virtual Memory available. It's that which needs addressing, not the OS's bitness.
I am not getting any error. I have enough virtual memory, it's the physical memory that's lacking. As a consequence, my system is slow and spends a lot of time paging.
3) you would have to do a clean install to convert to 64-bit - and source the proper drivers (if they actually exist) yourself.
I know. They do exist.
