Laptop once a month or 2 PC (had 3-5% space remaining on C drive for the last 2 years... no point defragmenting that)
depends. In XP after adding or removing a large file or program. vista can defrag more file types than xp, win7 can defrag even more file types and auto-defrags in the background. Much better defragmenting in Win7, this is scheduled by default to defrag 1am Wednesdays in Win7. I haven't changed this setting, sometimes my computer isn't on all night, or if I install a large game in Win7 I defrag, overall I'd say once a week in Win7 as it is configured to do by default.
why people say once a week is enough? maybe for them but if you run too much data and you install and uninstall a lot you need to run a defrag at east twice a week
True, some people say once a month, thats too long even for normal use, the HDD gets fragmented extremely fast
Well your computer specs says all, you are having a gaming computer and this means installing heavy games, making images of them,saving checkpoints and so on... and this makes your HD fragmented so it is more often for you. But for some of them computers are mainly used for daily work so it isn't required for them. I too have a gaming computer with same specs as of yours(accept the large LCD screen and backup battery ) I have to defrag it quite often like once in a day and sometimes even twice