This problem was supposed to have been solved with service patch, but
still we have the same problem.
We cannot install the agents on clients when the regional settings are set
to Turkish, the issue is that (I have done many tests)

-A fresh install of Windows XP sp2 with all updates using English for
regional settings and after the installation, re-boot the pc, change the
regional settings to Turkish, the client can be installed without problems.

-A fresh install of Windows XP sp2 with all updates using Turkish regional
settings, we get an error message when installing CASA.msi 1 of 35 (2 %).
Both installations are standalone installations.

So what method shall we use to upgrade our clients that run zen 7.0 with
all pc's with regional settings set to Turkish ?