I have a Dell Inspiron8100 laptop computer and Desktop
 computer both with USB ports and connected with a two way
 USB cabel,running Windows XP and Redhat Linux 7.2.I want to
 make it possible to transfer some files (size approximately
 of 100Megabytes )from the laptop to the desktop computer.I'd
 like to know how and what kind of software do I need for
 this?I'd like to know also is it possible to achieve this
without buying an extra hardware?

fdisk
or cfdisk under Redhat

 ne mi e qsno zashto si pishesh zaglavieto na bg, a vyprosa
 na eng, no karai. oshte po-neqsno mi e tova za fdisk nqkakyv
opit za humor li e ili shto li?
 ta na vyprosa: usb kabelite za vryzka na dve mashini ne sa
 prosto kabeli, ami si imat edin vid mrejova platka v tqh, ta
 syotvetno si iskat driveri. kato za nachalo trqbva v kernela
 (ili na moduli) da imash CONFIG_USB_USBNET, a veroqtno i za
 syotvetniq chip - naprimer CONFIG_USB_PLUSB, ako e napraven
ot Prolific ( http://www.prolific.com.tw/ ).
ako ne e toq, trqbva da se pozagledash koi e.
 tova e za dve linux kutii, za win pak si trqbva driver,
koito veroqtno si go imash na setup disk.

ghr --:))
absolutno si prav 4e e humor ... abe to ne e samo humor ...
ama to4no toz "vypros" mi izpluwa v glawata... 
"shto na English ??" 

 i taka shto na english li? ami celta e spestqvane na vreme,a
 ne myrzel i postnah tova v drug forum- ne na bylgarski sait
 i go paste-nah tuka,tyj kato precenih che bylgarskoto
obshtestvo e donqkade gramotno..

 e to xybavo ama naj ot gore na sita pishe linux - za
bylgari
 poneje vsi4ki u4im anglisjki za towa amerikancite ne y4at
4ujdi ezici.....