c# xls and xlsx file import

I want to load xls and xlsx file in c#. For xls I'm using:

Provider=Microsoft.Jet.OLEDB.4.0;
Data Source=;Extended Properties=\"Excel 8.0;HDR=YES\ 

For xlsx :

Provider=Microsoft.Ace.OLEDB.12.0;
Data Source=;
Extended Properties=\"Excel 12.0;HDR=YES\ 

once the projects platform target was Any Cpu I can upload xlsx file without problem but when I upload xls file I got the following error:

"The 'Microsoft.Jet.OLEDB.4.0' provider is not registered on the local machine."

And if I change the Platform Target to x86 then xls file is uploaded without problem but this time xlsx file is giving this error:

"The 'Microsoft.Ace.OLEDB.12.0' provider is not registered on the local machine."

How can I upload but file formats without error?

Thanks

Tags: C# (C# 4.0), Microsoft Excel