Vista only reporting single core on Mobile Sempron 3500+

Hi, I have an annoying little problem I’m hoping someone can help with.  I’m going to be as thorough as possible, so as to save everyone the trouble of suggestions I’ve already tried.

I have an Inspiron 1501 with the Mobile Sempron 3500+.  The problem is that Windows vista is only reporting this processor as a single core.

When I originally got this laptop almost 2 years ago it came with vista, and with only 512mb of memory I found myself unwilling to give vista a good trial run.  So I downgraded to XP within 2 days of ownership.  I never had a problem with XP, but I decided with more memory and recent SP’s vista might be worth trying now.

 I formatted, and repartitioned the drive, and installed vista.  Vista has been running….kinda ok.  Not really impressed, but I noticed that it’s only reporting a single core.  AMD claims the Mobile Sempron is a dual core, the laptop was plastered with stickers stating dual core, and so on. 

I’ve checked the web, and found solutions ranging from deleting the old HAL file, and replacing it, to setting detect HAL in MSCONFIG.  I have tried to detect HAL in MSCONFIG, and it doesn't seem to make a difference.  I haven’t tried deleting the current HAL, since I did not upgrade, and the build should have been specific to this machine at the time of install.  I have also tried uninstalling the current processor in the device manager, and restarting so it could detect the current CPU, and this also did not work.  I also only have 1 window for CPU performance, in the task manager and there's no option available to view the cores individually.

 In the device manager I do NOT see more than 1 processor listed in the processor group like many other people who have a similar problem do.

So, I’m wondering….Does anyone have any ideas for me?  I’d hate to think I bought a laptop that I’m only getting half the benefits from.

Thanks in advance   :)