Being a kinda newbie, I have been running my computer believing it is a 32-bit machine-now I am in doubt....
Can someone tell me exactly whether my PC is 32 or 64 bit?
PC= HP Pavillion a810n AMD Athlon 64 3300+ processor, 1GB RAM, 160GB HD.
Originally it was running XP SP3.
Can I enter a command into the terminal to output my exact hardware??
See this..

-Processor-
Name : AMD Athlon(tm) 64 Processor 3300+
Family, model, stepping : 15, 12, 0 (AMD Opteron/Athlon64/FX)
Vendor : AuthenticAMD
-Configuration-
Cache Size : 256kb
Frequency : 1800.00MHz
BogoMIPS : 3616.76
Byte Order : Little Endian
-Features-
FDIV Bug : no
HLT Bug : no
F00F Bug : no
Coma Bug : no
Has FPU : yes
-Capabilities-
fpu : Floating Point Unit
vme : Virtual 86 Mode Extension
de : Debug Extensions - I/O breakpoints
pse : Page Size Extensions (4MB pages)
tsc : Time Stamp Counter and RDTSC instruction
msr : Model Specific Registers
pae : Physical Address Extensions
mce : Machine Check Architeture
cx8 : CMPXCHG8 instruction
apic : Advanced Programmable Interrupt Controller
sep : Fast System Call (SYSENTER/SYSEXIT)
mtrr : Memory Type Range Registers
pge : Page Global Enable
mca : Machine Check Architecture
cmov : Conditional Move instruction
pat : Page Attribute Table
pse36 : 36bit Page Size Extensions
clflush : Cache Line Flush instruction
mmx : MMX technology
fxsr : FXSAVE and FXRSTOR instructions
sse : SSE instructions
sse2 : SSE2 (WNI) instructions
syscall : SYSCALL and SYSEXIT instructions
nx : No-execute Page Protection
mmxext : Extended MMX Technology
lm
3dnowext : Extended 3DNow! Technology
3dnow : 3DNow! Technology
up

Your CPU is both 64 and 32 bit capable.

Wikipedia is always worth a try.

http://en.wikipedia.org/wiki/Athlon_64

OK, so according to the Wiki-I can run both 32 and 64 bit OS, programs, etc.?
Athlon 64 3300+ 2 2400 MHz 256 KiB 800 MHz 12x 1.50 V 89 W Socket 754 ADA3300AEP3A

http://en.wikipedia.org/wiki/List_of...rocessors#fn_2

Well, I am running 32 bit versions of Linux now-what differences would there be if I install a 64bit Linux system?
Can I have both 32 and 64bit Linux distro's installed?

No much and you can

Unless you are taxing your system with work station stuff, a graphics design program or some large numerical computation, you should see no performance difference between a 32-bit and a 64-bit installation.

If you mean dual or multiple booting of linux distros, the distros use the hardware each on their own terms, just as Windows would in a dual boot. I don't know about one dealing directly with the others files, say if one wanted some files, a /home perhaps, to be common to both 32-bit and 64-bit distros, without the use of Samba in some form. I know nothing about Samba beside what I can read in a description.

Just for the record, it is the "lm" flag in the capabilities list for your cpu which tells us that your cpu is capable of running 64 bits software.

You can run a 64 bits OS without a problem. You can also run 32 bits (x86) software under x86_64 as long as all the required libs are there for 32 bits as well. You can't run programs compiled for x86_64 under a 32 bits OS, though.

You won't notice that much difference in most applications, but there should be no downside either. You can also dual boot as many distros as you want, and have 32 and 64 bits distros installed alongside.

You could run either 32 bit or 64 bit Linux. A few programs are a lot faster in 64 bit. But most programs are a little slower in 64 bit primarily because of increased cache misses.

That's a small L2 cache by the standards of current software. I think that will magnify the disadvantage of 64 bit.

64 bit still wouldn't be terrible. So if you have a specific reason for wanting 64 bit, don't get scared away by a modest slowdown.

Even with the smaller cache I wouldn't expect the programs that are slower in 64 bit to be a lot slower. If you are running one of the few programs where the 16 sse2 registers make a big difference, those can be a lot faster in 64 bit.