1 Megabit = 131,072 bytes
1 Megabit = 128 KB (kilobytes)
2 Megabits = 256 KB (kilobytes)
This is simple math guys.
A 100 Mb ethernet port has a mathmatical limit of 12,800 KB per second thru-put. That's 12.5MB per second - or a 600MB CD in 48 seconds. Of course it will never achieve this due to the way networks operate, but we're talking math here.
The 100 Mb connection reported by Windows is that from your PC to the router. The upstream connection on DSL cannot be this fast, it's far more likely to be either a 512, 1 or 2 Megabit connection. Maximum possible speeds for each:
512 = 64 KB/s
1 Megabit = 128 KB/s
2 Megabit = 256 KB/s
(Using binary assumptions for rounding)
If as he said he has a 512 connection, then you're looking at an absolute maximum of 64 KB per second downstream. This of course doesn't take into consideration any of the packets required for the network negotiation, it's just a math limit.
However there are other factors influencing the perceived download speed, including the files contents.
As usual Google knows the answer to this one - just type the following into its search box:
'how many kilobytes in 2 megabits?'
'how many bits in a megabit?'
'how many megabytes in 2 megabits?'
etc etc etc
Google calculator rocks
Exit Planet Dust