Can you meter the voltage giving you the shocks? As you are alive and typing, I guess it isn´t 240V?
If it IS 240V, somewhere in your power setup "zero connector" and "phase" may have been exchanged by mistake. Any voltage on a chassis, that should usually carry zero or "ground" is really hazardous unless you consider a rubber carpet for your place. You should check everything from the wall outlets on with a "phase detector".

Sounds like you're discharging static from the carpet through the equipment into ground.

If you're only shocking parts connected to an electrical ground (the chassis, the outer part of USB connectors, the rims of d-sub connectors, etc), you're not damaging anything. Just make sure you ground yourself before doing anything with the internals and you'll be fine.

Like 24bit says, but rather than spending too much money, you can pay an electrician to do this for you. It's compulsory in manyh countries to have all electrical applicances tested like this before you rent out a property. Aside from a small call-out charge it's about £2 for each appliance test - that is an appliance with a mains plug.

But I suspect it's your carpets too, and you're just earthing static on you when you touch it. If you have a modern electrical RCD switch unit (and the UK seems to be the only place that has adopted these) then the RCDs should reset when they pick up any current on Earth / Ground, or any contact between Neutral and Earth - a pain when you're trying to wire up devices without reseting the circuit (it's ok, using a sparky screwdriver).

In Germany, a residual-current device (RCD), or residual current circuit breaker (RCCB) has been introduced with DIN VDE 0100-410 (2007-06) in 2007. For the time being, the devices are obligate only for outdoor power plugs and bathrooms, where you are easily grounded.
Dougal´s computer room seems to apply to this too

BTW: There are little isolated srewdrivers with a tiny "lamp" in the handle, that will glow if it touches a phase. How do you call those in English? In German its "Phasenprüfer" and dirt cheap.

What country are you in? What's the condition of the wiring in your house?

@24bit,

It's called an Electricians Screwdriver, or a sparky screwdriver. I used to be in the trade many years ago - arounf the time of the Mac LC III. These screwdrivers are relatively cheap, about £10-£12 for a good one, I seem to have built up a collection of four by now - I found two at the last house I rennovated, it's amazing how many tools you find under the floorboards from previous trades, screwdrivers, chisels, etc. anything that can can be accidentally knocked into a space made by a lifted floorboard. Never found any bank notes, or Mac II's, not even a Mac Pro
But for an electricians screwdriver, you have to hold them in a certain way for it to work, so test it first on a known live source, every time you use it.

Those ¨Electricians Screwdrivers¨, in my country they´re called Buscapolos (they flash a light if it touches any electric flow by pressing your finger over the top of the screwdriver).
The more intense the light, the high voltage you´ll have to deal with.

I do have to restore the 3 legged plug with electrical grounding when i get some touches from the aluminium case of my G5 (wasnt that funny... we re using 220v over here)
Then i discover that i was very charged with a electro-estatic charge, and the safest way for my computer to deal with it is derivating the charge to the ground.

You need to check if your electrical wiring (at ur house) is grounded, and then use the three-pins plugs-to wall, always.