OK I have a machine sitting here presently running Vista Home Premium, It has a dual core Athlon 64 on an Asus M2N-SLI deluxe board with the most current bios
I just dropped 4 gigs of ram into this thing and was aware of the address limitations of a 32 bit os
Both xp pro and Vista HP 32 bit can only address 3.5 gigs of ram
This is why I want to run vista HP 64 bit, I can get it at a good price but I need to know this

I love Firefox and Thunder bird and I was wondering if they would run on this, I also need to run the Second Life viewer since I have an account with them
Can Vista 64 run 32 bit apps, I remember Win 9x would run 16 bit apps , is it done in the same way

Heres my specs

Asus M2N-SLI deluxe mobo
Amd Athlon 64x2 6000+
4 gigs Mushkin ram
Evga gforce 8800gts 640 meg only one card
XFI extreme music sound card
500 gig seagate sata 2 hd
Samsun dvdrw drive
Gosh and a floppy drive

I know there are 64 bit drivers for my components I am just concerned about my apps

Thanks in advance