why does ubuntu see 2 cpu when i have only one?

Could you please post the output of the following two commands? Perhaps your CPU supports Hyper-Threading.

# cat /proc/cpuinfo
# top -b -n 1

here the info -- hope it helps. -- i saw that it says 'siblings' - does that refer to a multi-thread feature of pentium 4? and is that used in the linux kernel?
(i appreciate if you point me to the literature)

thank you

andrew
-----------------------------------------
processor : 0
vendor_id : GenuineIntel
cpu family : 15
model : 3
model name : Intel(R) Pentium(R) 4 CPU 2.80GHz
stepping : 3
cpu MHz : 2793.244
cache size : 1024 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 1
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 5
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe constant_tsc pni monitor ds_cpl cid
bogomips : 5590.61
clflush size : 64

processor : 1
vendor_id : GenuineIntel
cpu family : 15
model : 3
model name : Intel(R) Pentium(R) 4 CPU 2.80GHz
stepping : 3
cpu MHz : 2793.244
cache size : 1024 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 1
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 5
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe constant_tsc pni monitor ds_cpl cid
bogomips : 5586.50
clflush size : 64

---------------------
frank@dresdenG:~$ top -b -n 1
top - 17:17:49 up 57 min, 1 user, load average: 0.05, 0.13, 0.08
Tasks: 115 total, 1 running, 114 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.3%us, 0.2%sy, 0.0%ni, 99.0%id, 0.4%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 1034812k total, 433268k used, 601544k free, 9852k buffers
Swap: 1510068k total, 0k used, 1510068k free, 245784k cached

  PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
 5504 frank 15 0 45976 27m 8552 S 4 2.7 0:01.93 nxagent
 5721 frank 15 0 2360 1052 784 R 2 0.1 0:00.01 top
    1 root 15 0 2952 1852 532 S 0 0.2 0:01.36 init
    2 root 11 -5 0 0 0 S 0 0.0 0:00.00 kthreadd
    3 root RT -5 0 0 0 S 0 0.0 0:00.00 migration/0
    4 root 34 19 0 0 0 S 0 0.0 0:00.00 ksoftirqd/0
    5 root RT -5 0 0 0 S 0 0.0 0:00.00 watchdog/0
    6 root RT -5 0 0 0 S 0 0.0 0:00.00 migration/1
    7 root 34 19 0 0 0 S 0 0.0 0:00.00 ksoftirqd/1
    8 root RT -5 0 0 0 S 0 0.0 0:00.00 watchdog/1
    9 root 10 -5 0 0 0 S 0 0.0 0:00.02 events/0
   10 root 10 ...

It's not a bug, it's a feature. :)

You see 2 processors, because of the hyper-threading technology from Intel. You can read more about this here:
http://en.wikipedia.org/wiki/Hyper-threading

And I don't see an excessive CPU load in your top output.