This has mainly to do with the number of memory address lanes available to the system, and how the OS uses and addresses the memory itself. But first off - if you have 4GiBytes of Memory in your system, chances are you will see only 3.25GiBytes available.

This is mainly due to the fact, that all PCI/PCI-eX Devices allocate some memory for mapped IO Calls / DMA accesses, and to be able to access this reserved memory in a linear way, you need to be able to talk to these in 32 bit mode - thus the 4GiBytes limit. Note that the missing memory has been mapped by the physical extension cards starting from the upper 4GiByte limit downwards. Means the more memory a card allocates and the more extension cards you have, the more memory will be missing.

Even on 64Bit CPU/OS's combinations you may see this beheavior. Many extension cards still use 32Bit registers. These can only address the first 4GiByte linearly, thus allocate memory from 4GiByte on downwards - recreating the problems due to backwards compatibility. 

 The mp3streamer is a very old code and was meant to be used internally (LAN) only. As it has seen no code submission over 10 years, the code has been removed from any system. Please find an alternative on the Internet... There are many.
Please remove any link you may have found. 

 The 3dpixmaps icon collection was put together back in 1998 to use on the Desktop of the Technical University in Berlin. It was later used by the SuSe distribution in conjunction with the fvwm Window Manager.
As that is a very long time, and the internet has developed quite many new icon-sets, this package can now retire.
Please remove any links you may find.