Plz also tell me that in devloped country what are they using computer and what system they are applying.(As example in our developing country like india pakistan banglaedes mostly use window 95/98 or 2000 and Xp and mostly accounting wrok we do on Excell etc.
If you need an office suite, you can use OpenOffice which can read in most Word/Excel/Powerpoint files, stores files natively in .xml, and can write out most Office formats for interchange.
If you need a browser, you have the most excellent Firefox (same versions as on Windows).
If you need e-mail, there are a number of POP/IMAP clients as well as an Exchange client.
But you have ab option like MacOS also.