folder redirection of C:\WINDOWS\Installer

I'm configuring an Asus eeePC, 4 GB SSD (C and 8 GB SDHC (D. The
system sees both as fixed drives.

I'm working to remove folders from the small C: drive to the much
larger D: drive. Using sysinternals JUNCTION.exe I've created symbolic
links, to wit:

C:\WINDOWS\Installer --> D:\WINDOWS\Installer
C:\MSOCache --> D:\MSOCache

The re-directed folders work OK when the OS (XP w SP3) handles
requests for existing files.

However I've witnessed one MSI Installer installation where the
symbolic link C:\WINDOWS\Installer is removed and replaced with a
folder then populated with the app's .msi installation database file.

I've spent several fruitless hours searching for means to make the
symbolic link permanent.

Any suggestions how to make the symbolic link permanent?

Cross posted to microsoft.public.windowsxp.customize and
microsoft.public.windowsxp.general

Thank you,
Harry Jacobson