Because you went from 64bit to 32bit. There is a cap on the amount of ram that 32bit machines can access...
I got an Acer Aspire 5738z with 64bits windows 7 but after realizing that is was not detecting internet connection i decided to format it and replace the window 7 with vista ultimate 32bits, i lost most of my drivers which i just recently download on www.acer.com but now, vista show my RAM as just 3GHZ, why? on this same machine ,i have ubuntu which say it is 4GHZ ram present there.On my machine set up it read 4GHZ, where does the other part of the RAM gone to in Vista.
I need explanation and help to make it show 4GHZ on system properties

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