some questions on my new ndsl:

1) when charging power, should i remove the flash cart?
2) hori screen protector, how to properly apply it on the screens? seem that it is not really sticking well to the screen, got some 'bubbles'...i already press it flat to the screen...

You don't need to remove your cart, you don't want dust entering the Slot-1 compartment.

As for the screen protector, I'm not sure how to as mine came pre-applied to it. Just make sure to use good tape to strip off the dust, and use a credit card and start from one side, slowly easing and kneading the air bubbles away.

more questions...noob haha...
1) can i just off the DS when in middle of playing a game? will it spoil the cart? or the DS itself?
2) when i open the DS to the max, it will got this 'tack' sound on the hinge...issit normal? looks like if do like this thousand more times, afraid the hinge will eventually crack...
3) will the touch screen become LESS responsive over time?

So far I've never seen a game which the game will automatically shut off your DS. In other words, it should be perfectly safe, except during saving. The 'tack' sound you hear is normal, I have that same click on mine too.

I own a touchscreen PDA which is already about more than 10 years old, and the sensitivity has never diminished.

1) Yes you can. BUT you can't off it during saving. That will spoil the save file
2) Yes it is normal
3) Yes it will be. But this is based on how vigorous you tap the screen. If you tap it like hitting the drum box. Your screen will be pretty screwed.

Hi there! (Hey Colin! Wah... almost like a moderator on this thread ah!)

Anyone knows if a microSDHC will work on my TTDS? currently using a 1gb microSd...want to upgrade to an 8gb one..but after 2gb..the only ones are in microSDHC format.

LOL, just sharing what research that I've done since I got my DS recently

DSTT supports SDHC, so it shouldn't be a problem at all.