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Normally, C:\ partition is supposed to have at least 20 GB or 10% free space for system operations like creating restore points and for paging.
Microsoft Visual C++ 2005 Redistributable KB2467175 is a security update for Microsoft Visual C++ 2005. Microsoft Visual C++ 2005 is a runtime library that many programs depend on. If you are planning to remove the installation files (deleting from temporary location), it is safe. But, if you are planning to remove it through Programs and Features, programs depending on this library will fail to run after removal.