change hardware, that include change power supply from AAA to AA, or overclocking, or LCD backlight.... Or you mean to the whole hardware..... anyway I haven't do any of these ones, u have to b pretty sure of what u are doing or u will mess with the calc....

It probably includes any of those things you mentioned, not just replacing the entire insides of the calc.

Actually, you gave me an idea, mentioning switching from AAA to AA...I've seen a guide on modifying it, but it'll be thicker than before and the battery case won't fit on (of course). However, I wonder if it would be possible to make it still take up the same amount of space by hollowing out the bottom of the battery holder, using only 2 AAs, and adding a small boost converter...

AA's last almost double the time, i would gladly sacrifice size for battery life

It's actually not that hard, if you don't care how it looks. You just need to get an external battery case that fits AA batteries, and attach wires to the ends of the external battery case's metal things on the end that are meant for that and to the calculator's battery case, where normally the ends of the battery would go. Alligator clips work better than regular wire, but you can do it with either one.
The only problems with that are that you get exposed wires and that you have a very awkward arrangement of parts outside of the calc. I have never tried doing that with my calc, but I have done it with small electronics--my computer's speakers, a booklight, et c.

I don't really care about how it looks, the reason I don't want it any larger is because then it won't fit in my pocket. ;-)

wouldn't that sort of defeat the purpose of using AA's though cause I doubt that you would get much improved battery life.

I tried adding a backlight to my 84+SE's LCD...The LED went in all right, but I found that I couldn't get it to shine through the clear plastic of the LCD itself. And, there is no room to add additional plastic sheets due to the link ports at the top :-( Plus, the LED drained my batteries rather quickly...However, the calc was not damaged, so I voted "Yes, for the better"!

Would it be possible to mod a Game Boy worm light to commect to the USB port of a TI-84+(SE)?

You could do it with a lot of soldering, but it would still drain your power really fast. Plus if you messed up you ruin a mini-USB plug and a wormlight.

What I had in mind was refitting the worm light with a new USB potr thar with the calc, like cutting off the end of a calc to calc wire and soddering it to the wotmlight wite, of course after cutting off the end of the wormlight.

Overclocking?

Yeah, there's a well-documented resistor/capacitor pair for each calc that controls the processor's clock speed, so by replacing the capacitor with a lower value you can make it run faster. You can also replace the resistor too, and IMO it seems easier, but most people replace the capacitor.

Why would one want to make the clock run faster? Or am I mistaken and it makes the calc run faster?

Overclocking is the process of making a CPU run faster than it's supposed to. In this case, by modifying some resistors, one can increase the speed of a calculator by 3-4 times. The clock speed refers to a measurement of the speed of a CPU (this time in MHz).

Aaaaaaaahhhhhhhhhhhhhhhh.
Got ya.

Doesn't that mean that there's a risk of the processor overheating? It may not be much with a z80, but there could be some negative effects associated with it.

Right, no chance of overheating with a Z80 (it only gets overclocked to ~24 Mhz anyways, at least for an 86). The "negative effects" are that if you push it too far beyond what the processor was designed for, it might cause timing problems and start acting strange. Oh, and Mario will run four times as fast, making it hard to get through levels...

...and battery life decreases linearly with processor speed increases.

Does changing the batteries count? :-P

I would say no, but it is changing parts enclosed in the calc...

and yes, I know you are joking. <:/