SR45, the Dimension 4600 did offer HT although I don't know why it is causing problems for the original poster in this case.  If you check the User Guide, the HT settings are listed in the System Setup Program section under the CPU Information option of the BIOS.

I know that the Dim 4700 system on up has HT, but not supported in the 4600, and below systems.  User Guide does not show it has Hyperthreading either. 

 

 

Dim 4400
2.6 Ghz 400 FSB
1 Gb 2100 DDR memory
Windows XP Home
120 Gb Seagate 7,200 drive
24 inch 2407 WFP
XFX 7800 GS O/C AGP
16x DVD-R
410 watt ( PcPower&Cooling )

Thanks Majestic, found these two links.....

 

These two links I found from another thread discussed that HT is a go for the 4600, but again not possitive as to why the OP is having issues. 

 

http://www.dellcommunity.com/supportforums/board/message?board.id=dim_upghw&message.id=30135&query.id=469883#M30135

 

http://www.dellcommunity.com/supportforums/board/message?board.id=dim_upghw&message.id=46293&query.id=469883#M46293

SR45, I've helped people in the past with the HT setting on the 4600i and it worked for them.  From a BIOS stand point it looks like the OP is using the latest available version so that rules that out.  Quite possibly the OP system is having a conflict with an application that is running in the background when HT is enabled.

 

Cable007, just for the heck of it try enabling HT and then boot Windows into Safe Mode.  If you can navigated around for a while in Safe Mode without any problems then try booting into the normal Windows, but disable any unneeded applications running in the background.  If the system works Ok then one by one enable an application until the problem returns.  That would at least give you an idea of what is causing the problem.

ok thanks I do that...

Thanks again Majestic    :smileyhappy: