If I double-click ahc.exe or select Photoshop Help I get two nasty dialogs. The first simply says "The operation could not be completed." and the second says "The instruction at 0x00864a4d referenced memory at 0x01040b08. The memory could not be written."

I'd be interested to know what's broken and the most expedient way to remedy this. Thanks.

Best,
Eric
Photoshop CS2, WinXP Pro, dual Xeon, 3G.

There are two techdocs concerning Help Centre Problems:

332006 Error "Model subsystem error: 1016" when you start Help
Center from any CS2 application
http://www.adobe.com/support/techdocs/332006.html

331717 Help window doesn't appear when you start Adobe Help Center
(Windows XP, 2000)

http://www.adobe.com/support/techdocs/331717.html

Neither of which address this specifc problem, but could be worth your
while to read through.

Also, it may be worth trying the following:

Assuming ahc.exe is located in C:\Program Files\Adobe\Adobe Help Center,
delete the following folders

C:\Program Files\Adobe\Adobe Help Center\AdobeHelpData\Cache
C:\Program Files\Adobe\Adobe Help Center\AdobeHelpData\Database
C:\Program Files\Adobe\Adobe Help Center\AdobeHelpData\Preferences
C:\Program Files\Adobe\Adobe Help Center\AdobeHelpData\Search

The only folder under C:\Program Files\Adobe\Adobe Help
Center\AdobeHelpData you should have left is one called packages.
Run ahc.exe
What should happen is that your help center database should get rebuilt
(you will see progress messages as it process each help package) and
everything should work.

PSmeiles
I experienced the dreaded Adobe Help Center "ahc.exe/0x00864a4d" problem in CS2/WinXP. I followed tips here on the posts. No good. I couldn't install the AHC.exe 2.1 due to error 1722. I tried a full uninstall/renstall twice and received the error repeatedly. I installed the new MS installer. Still no go.
Finally, I deleted the entire Adobe Help Center folder and reinstalled the entire CS2 suite over top of itself from Control Panel. Perhaps somebody can tell me why this worked when a full uninstall/reinstall didn't?