Trying to speed up lightweight distro on old computer

I'm trying to install a lightweight distro on my sister's old desktop. It has a Celeron 3.06Ghz processor, a 80GB HD but only 432 MiB RAM. With these specs I thought antiX-09.2.1_386-base was my best option but it is mind bogglingly slow even before firefox is launched and she would also like me to install Thunderbird... I know there have been similar questions in the past and I'm willing to try all suggestions in the answers. However when I run

-class cpu

it says something about a cpu 0 (which is the Celeron) but also gives me

-cpu 1 : DISABLED

As per request the full output of

-class cpu

is:

lshw -class cpu
  *-cpu:0                   
       description: CPU
       product: Intel(R) Celeron(R) CPU 3.06GHz
       vendor: Intel Corp.
       physical id: 4
       bus info: cpu@0
       version: 15.4.9
       serial: 0000-0F49-0000-0000-0000-0000
       slot: Socket 775
       size: 3066MHz
       capacity: 4GHz
       width: 64 bits
       clock: 133MHz
       capabilities: boot fpu fpu_exception wp 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 nx x86-64 constant_tsc pebs bts pni dtes64 monitor ds_cpl tm2 cid cx16 xtpr lahf_lm
       configuration: id=0
  *-cpu:1 DISABLED
       description: CPU
       vendor: Unknown
       physical id: 5
       bus info: cpu@1
       version: 15.4.9
       serial: 0000-0F49-0000-0000-0000-0000
       slot: Socket 775
       size: 3066MHz
       capacity: 4GHz
       clock: 133MHz
       capabilities: ht
       configuration: id=0

Does this mean there is a second cpu (core) that can be activated? Can anyone shed some light on this as both the internet and this website's search function seem to come back empty handed. Stay safe and thanks in advance.