I checked for hard disk on gparted (lenny) it just shows 233 gb in total (including swap) while mine laptop has 250 gb what happens to rest 17 gb ??

Common misadvertisement, if you look at the hard drives manufacters website, or product page you'll likely see 1GB = 1,000,000,000 bytes however in truth 1GB = 1,073,741,824 bytes. Thus 7.3% is lost by a misadvertisement. Their is nothing to worry about it really, it's very common and almost all hardware vendors do this dispite the fact it's completely inaccurate and did leave them slightly vunable from a legal point of view (because of the mis-advertimsent). However rules were taken and the more annoying thing came about of referring to GB = 1,000,000,000 was made, even tho such a number is nusiance in computing because it is not a direct power of 2...

http://en.wikipedia.org/wiki/Gigabyte

Fairly good source.

COOL ! So simple thanx

Not correct, really. The hard drive manufacturers are 100% right. Kilo means 1000, Mega means 1,000,000 and giga means 1,000,000,000. Evidence: 1 kilometer = 1000 meters, 1 kilogram = 1000 grams, etc. The conception that we should use 1024 as a base derives from the RAM manufacturing industry, where the standards are not kilo, mega and giga but KIBI, MEBI and GIBI (thus: kibibyte, mebibyte and gibibyte). If anyone runs a risk of legal claims for misadvertisement, it is them. Then again, who would push charges for getting more than advertised...

The terms as whole words were created by technician's... so the original meanings were 1024 at each increment as a defined standard.

No they are/were not... These terms have been IEC/ISO/IEEC standards for the last ten years - before that, the 1000/1024 pairs were used interchangeably, without there being any clear definition at all. However, ten to the third power has always been the rule in both storage and CPUs (how many Hz is a megaHz?).
Hard drive manufacturers have been the subject of litigation in the past and they have repeatedly been cleared of all charges. Your are only adding to the general confusion.

The general confusion was caused because orignally it was 1024. However because of the looseness of the term, hardware vendors turned around and outputted 1000 instead of 1024 so they could sell effectively less for more money, but meh~. Generally the industry to move over to MiB and GiB. 1000 is a nusiance number as far as computing goes as it's not a direct number you can get as a power of two, also as far as I am aware, in RAM most vendors still use 1024 as well, it was only the hardware vendors trying to trick people out of the effective storage in the first place that truly caused any issues... As for Hurtz, you could say a Hurtz is a scientific term, not a technical term~. Kilo, Mega and giga do mean thousand, million, so from that point of view it is right, but it wasn't how the figures were original defined for a measurement of storage.

Companies using technicalities and confusing the entire industry is common and shouldn't be accepted, you get similar confusions with hubs, switches and routers these days since different companies claim them to be different things and now the lines are so blurred the hardware manufactures get away with defining it however they want.