Thanks a lot guys. I'm 15 and I don't know much about this stuff. Thanks again, you really helped me alot.

EDIT: Gabby131, how do you have 64gb of memory on your n900?

IMHO Overclocking per se is not a bad idea, if the operating voltages, and resultant heat generated are within limits.

Infact most multi-core desktop CPUs automagically overclock a few cores when needed I saw this on my Phenom II X6 1055T ( Turbo Boost)

In case of N900, try to find the maximum MHz for the voltage i.d. of 60. Usually it can work at 1000Mhz with votage ID 60, i.e. approx 1.35Volts.

Running at more than 1.35Volts is probably going to accelerate damage to the CPU.

Two things can happen:
One is stability issues and data corruption. Every chip got some critical paths where the signals take a certain time to pass. If the clock is too fast, the signal may not make it in time before the next clock tick, which may result in data corruption. Lower voltage may further increase instability.

The good news is that most chips have a wide margin of error, especially for low power chips such as ARM Cortex-A8. This means that overclocking the chip by 50% is usually safe. However, this is individual, since some chips have tiny "defects" that do not affect the chip at normal speed but can cause data corruption when overclocked.

The other thing that can happen is that the heat produced by the chip is increased, and as a result, it would die sooner than it would at normal speed. In practice, if you overclock it by around 50% and lower the voltage, physically damaging the chip is much less likely than causing stability issues.

He meant storage. 32GB onboard + 32GB MicroSD card.

to OP: Although theoretically damage might occur and people here are fair enough to point out to that possibility, it seems to me like highly unlikely.

Looking back I notice I have been overclocking computer things since the year you were born and I was always happy to have extra performance to be cutting edge which is just a word for the latest outdated technology. Computers are never fast enough.
486DX50, Pentium 120, Pentium 166Mx, Celeron 300A and all successors AMD or Intel. S3 Virge videocards, 3Dfx videocards, Nvidia cards, routers, ... Never succeeded in breaking anything (except from a hard drive that couldn't keep up with the unlocked FSB)
The only thing you should care about imo is that the device continues to run stable in all circumstances to avoid data corruption.

Over here the temperature is currently 45 degrees and I carry my N900 playing a movie in while locked in my pocket on the bicycle or try to use it in bright sunlight to torture it in extreme conditions. Ideal profile 500 - 850Mhz seems reasonable speed and it is not less stable than to default config.

Exactly, that's why I use lv mode with limits 250 900 , works like a charm for almost two months

same here 250/900