The amount of RAM a computer can have is limited by the motherboard (something like 12 GB is reasonable), and the hard drive space is limited by how large they make them (something around 1,500 GB per connection available on the motherboard is reasonable)
1024
There are 1024 megabites in 1 gigabite. 20 gigabites has 20,480 megabites.
It depends on how many gigabites it has like 8 gigabites can hold about 15 movies.
None
5500
4500
4,000,000,000
100
a half
1.306728 gb
A lot.
It's about 652 Megabytes. Or, 0.652GB