I agree with that - having more memory in the machine than what you can actually use makes no sense at all.
But 512MB is not "much" in todays terms - which was my original point. The processor in manav's system is fast enough [assuming it's not also busy doing something else, so that's not the source of slow compiles]. Antivirus software and/or lack of memory comes up next on the list.
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Mats