Dual Xeon proc with HT enabled but only 1 processor works??!

[znewsokoban 0]

hi all, i have a dual xeon processors 2.4G and Hyperthreading

enabled, every thing was working fine , 4 graphs in the task manager,i installed S pack 2 and now i find my pc so SLOW and

when i check the task manager i find only 1 graph,

i checked the device manager and under computers it is:

ACPI Multiprocessor PC, i checked the bios and find HT enabled,

i checked number of processors (Device manager> processors) and

find it 4!! so what's going on, i have to say that for hardware

and setup i am a beginner so please help me and make it in details, thanks in Advance.