*.msi issues

My problem is this; when attempting to install the latest update of java
(version 6 update 16, in either 32-bit OR 64-bit flavours)
i recieve the error message:

Windows Installer
This installation package could not be opened. Verify that the package exists and that you can access it, or contact the application vendor to verify that this is a valid Windows Installer package

a search on this error message has turned up many many problems ranging back to xp, so i think i may be out of my tech depth here

I recieve the same error message trying to install Steam using the installer, however i was able to unpack steam using winrar but attempting this with java yeilds more error messages

I am running Windows 7 Home Premium on a machine i built myself, can provide spec if required

Help would be greatly appreciated

if more information is needed please can you let me know which info here are the system info specs
6.1.7600 build 7600
windows 7 Home Premium
GA-MA770T-UD3P motherboard
AMD Phenom II x4 945
2x 2GB 1333Mhz

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