Import from excel: the mixed colums issue

From the sas knowledge base I get some usefull information : TypeGuessRows

Basically TypeGuessRows is the number of rows explored by the driver to determine the type of the columns.By default it is set to 8.

I suggest to set it to 0, that is to explore all rows. This may lead to performance issue, but prevents data loss.
According to the cited article the keys are:

1. HKEY_LOCAL_MACHINE/Software/Microsoft/Office/12.0/Access Connectivity Engine/Engines/Excel/TypeGuessRows
2. HKEY_LOCAL_MACHINE/Software/Wow6432Node/Microsoft/Office/12.0/Access Connectivity Engine/Engines/Excel/TypeGuessRows

But I also find them :

1. HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\14.0\Access Connectivity Engine\Engines\Excel
2. HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Jet\4.0\Engines\Excel

The best is to scan the register searching : TypeGuessRows.