Trying out Vista.. Very slow.

DougEdey is on to something, actually. In theory 32-bit OS's can address all 4 Gb but for a range of complex technical reasons don't; instead the fourth 1 Gb part of the address map is reserved for various PCI hardware and the fourth 1 Gb RAM shunted further up the address map. In short:

Code:

Address Contents 
0x00000000 - 0x3fffffff Memory 
0x40000000 - 0x7fffffff More memory 
0x80000000 - 0xbfffffff Even more memory 
0xc0000000 - 0xffffffff Memory-mapped devices 
0x100000000-0x3ffffffff Where the *?#! did my last GB go? 

To accommodate this, some motherboards have options of getting around that in their BIOS to access that last 1 Gb of memory. In your case, it may confuse Vista no end.

 

Well, for my motherboard to "see" all 4gb of ram I have to turn on the hardawre memory hole option. With it off, the bios and OS only see 3gb. But surely that shouldn't matter if I'm using a 64-bit OS which can address much more memory locations?

 

It's not just the OS. It's also a problem within the BIOS that hasn't really been addressed properly. What used to happen on older boards (to disguise this) was that you would have 4 slots but could only use a maximum of 3GB, or 3 slots with a maximum of 4GB. Not 100% sure why this happens but my friend had a similar problem and found that if he dual booted he would have the memory hole off for XP and the opposite for Vista

 

Ah right, I thought that too earlier. Even though the manual says 4gb max, maybe thats not the best option.

I might give asus a call.