Per my earlier post please see the information from Intel.
http://www.intel.com/support/platform/ht/os.htm?
iid=ipp_htm+os&
Note: Information on Hyper-Threading Technology ? for
Intel® XeonT processors is available here.
Microsoft* Windows* Operating System Desktop Based PCs
The following desktop operating systems include
optimizations for HT Technology and are currently eligible
to carry the new Intel® Pentium® 4 Processor with HT
Technology logo:
Microsoft* Windows* XP Professional Edition
Microsoft* Windows* XP Home Edition
The following desktop operating systems are not
recommended for use with Hyper-Threading Technology. If
you are using one of the following desktop operating
systems, it is advised that you should disable Hyper-
Threading Technology in the system BIOS Setup program:
Microsoft Windows 2000 (all versions)
Microsoft Windows NT* 4.0
Microsoft Windows Me
Microsoft Windows 98
Microsoft Windows 98 SE
Linux* Operating System Desktop Based PCs
The following Linux operating systems include
optimizations for HT Technology and are currently eligible
to carry the Intel® Pentium® 4 Processor with HT
Technology logo:
Red Hat Linux* 9 (Professional and Personal versions)
SuSE Linux* 8.2 (Professional and Personal versions)
Red Flag Linux* Desktop 4.0
COSIX* Linux* 4.0
Note that while other Linux operating systems may have HT
Technology enabled, only the distributions above are
currently eligible to carry the Intel Pentium 4 Processor
with HT Technology logo. If purchasing a PC based on a
different Linux operating system, check with your PC
vendor to determine if the PC includes the necessary
system ingredients for HT Technology and has HT Technology
enabled.