ZB3 didn’t show up in my Add/Remove program list either. I just reinstalled it right on top of the previous install. Then it both showed up on the list, and the ZB3.1 update worked.
This didn’t work for me… I get an error (can’t remember right now…) and the install fails. Weird.
benr’s solution worked for me - ZB3 wasn’t showing in my add/remove programs either. Re-installed ZB3 over previous install, installed patch and it all works.
I had this problem at work too on XP.
My IT admin had installed ZBrush3 originally, logged in as the administrator. When he logged in as the administrator we were able to apply the patch.
Still no luck…
I can’t delete zbrush and do a reinstall…(it is not visible in add/remove programs)… I tried creating a new admin account and tryed the patch from there, nope… dragged and dropped Pixologic program files folder into the trash and tried running a new install of 3.0 and that fails… tried downloading patch again and that didn’t do it either…
No system restore points but one made just prior to installing zbrush3 are available!.. and attempts to restore to that point fail!
I’m think its like some kind of infection…
mr charles, this is certainly strange behavior. There should be an uninstall ZBrush icon in the start>pixologic menu. Do you not have that? Please feel free to contact us at 1-888-748-5967. 
Ryan
I couldn’t install the patch for the same reasons as I stated earlier, trying to uninstall it was unsuccessful (the link for uninstall doesn’t work, it says that i must have the program installed in order to uninstall it), so I just reinstalled zbrush 3 then the update and it installed without problems.
Hi all
I read through all the posts relating to the zbrush 3.1 update failing. I run XP Pro x64 (4Gb Ram, 2 x dual Opteron 275’s and Tyan Thunder K8WE S2895 Mobo) and have finally managed to apply the 3.1 update.
Here’s what I did. I was using the default User Account of Administrator and installed ZBrush3 and it was working aok. But the 3.1 update kept failing with the Windows Installer error. So I created another account (call it what you like) and logged out of Administrator and then logged into the new account.
ZBrush3 wasn’t showing under the new account, so I installed ZBrush3 again to the original directory (C:\Program Files (x86)\Pixologic\ZBrush3) overwriting the original install. Then applied the 3.1 update. It installed aok. Logged out of the newly created user account and back into the Administrator account and hey presto I have ZBrush updated to 3.1.
Let me know if it works for you or not …
Madcap
@madcap:
Hi, I had the same problem under Windows XP Pro x64 with all the Windows updates up to date and also the newest Windows Installer but wasn`t able to install the ZBRush 3.1 update under my regular account (with admin privileges)!
But your hint with the temporary new account finaly worked!!! 
Thank you very much for pointing that out and sharing it with us!
Nevertheless this is a very strange behavior! 
Your welcome - Glad it worked for you aswell. 
This is the error I got when i tryed to install the 3.1 patch…
This patch could not to opened. Verify that the patch package exists and that you can access it, or contact the application vender to verify that this is a valid windows installer patch package.
ZB3 works without the update… I would just like to update.
Running XP 32, Madcap’s solution worked great for me.
This thread hasnt seen much action recently. Just thought I’d relate my similar experience with update.
Installed Z3 from backup disk on my new laptop (clevo 901c quad - Love this rig!)
Z3 runs amazing.
Try to install update, get the same result as others i.e. Installer cant find program etc. (same as pic shown in previous post)
Decided to poke around and look at program details. i.e. right click on Zbrush.exe icon, select properties. Check version number and what did it say?
–> 3.1
So I started up zbrush, and low and behold it showed a 3.1.
Can I believe this, or am I still running 3.0? Is there any way to confirm I am indeed running 3.1?
Regards, James.
As long as you can find features (some are required to Donwload /install yourself) from following pages, you have 3.1
-Pixologix page :http://www.pixologic.com/zbrush/trial/
-ZBC Wiki page: http://www.zbrush.info/docs/index.php/ZBrush_3.1
Faster way to tell, if you can see ‘Zmapper’ button on upper left section on interface, it must be 3.1 since 3.0 didn’t support zmapper at all.
Malleable man - you are indeed running windows 3.1 then.
r