If you are already observing the error follow the procedure below to remove bad registry and reinstall agent on the machine.
Remove bad registry key on a machine you have physical access to
a. Copy the 'GHRegEdit64.exe' file from '\Program Files\Altiris\Deployment\Imaging\ghost\x64' to the 'NSCap' Share on the NS (Use GHRegEdit32.exe if the client with the error is a x86 machine. This is found under '\Program Files\Altiris\Deployment\Imaging\ghost\x86')
b. Go into the windows 7 repair command prompt (push F8 while windows is loading -> Choose 'repair computer' -> Choose 'Command Prompt')
c. Run 'wpeinit' to enable the networking before running the commands
d. Run 'net use y: /user:<Domain\User> \\<SMP-FQDN>\NSCAP <Password-for-User>'
e. Then Run 'y:\GhRegEdit64.exe delkey D:\Windows "HKLM\Software\Altiris\Altiris Agent"'
f. After this completes reboot the machine back into Windows 7 and verify the registry is accessible
g.Try installing the Management Agent once again and this time it should work
Remove bad registry key on a remote machine using Deployment Solutions
a) Copy the 'GHRegEdit64.exe' file from '\Program Files\Altiris\Deployment\Imaging\ghost\x64' to the 'NSCap' Share on the NS (Use GHRegEdit32.exe if the client with the error is a x86 machine. This is found under '\Program Files\Altiris\Deployment\Imaging\ghost\x86')
b) Assign a "boot to" task to the managed client and let it run so that it boots to automation
c) Once the machine is in WinPE use a run script task and run the following script against the client:
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net use y: /<Domain\User> \\<SMP-FQDN>\NSCAP <Password-for-User>
y:\GhRegEdit64.exe delkey D:\Windows "HKLM\Software\Altiris\Altiris Agent"
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d) Schedule a "boot to" task to reboot to production
e) Once back in Windows 7 check whether the registry is now accessible.
f) Re-push install agent from SMP console and wait till status changes to success.