i was wondering is it really possible to send a virus through yahoor other mails
Well yes and no .BECAUSE YAHOO AND other mail services scan your e-mail attachment for virus but having said that e-mail attachments has been the method of spreading a lot of viruses.So if you have an understanding of how anti-virus works you can code a virus to fool the anti-virus.Usually an anti-virus looks through the code and looks for pre-defined patterns in it's database and flags the program as virus if a match is found.
how can i protect my pc n how can i detect myself a file contains virus n how i can remove it myself if i dont have an antivirus
How can you remove it yourself ?? Install an anti virus.It's not that easy to remove a virus from your system because it keeps spreading to other files finally corrupting your OS which would require you to format and install fresh copy.Well usually virus are .exe files so unless you execute them you wouldn't know unless you are planning to open each .exe file and see what's inside.So it's always advised to have an updated anti virus installed.How do you detect if your system is infected??
Has your system been running slow ?
Does it behave in unexpected fashion ? These are some of symptoms anyways you can run a boot time scan to check if you are infected.
how do we make viruses actually????
Well use google .Numerous articles on this.Look in the code of some earlier spread virus like Happy99,Melissa.Here is llist of some famous virus.Use google try to figure out what they do
You will have to learn programming preferrably assembly(I recommend) or vb.net or any other to write your own virus.Be carefull while you code the virus you might end up deleting all data on your disk(I have done that by mistake) or anything else that might you didn't intend.
r there any books for all these thinks.
Lots of books and lots of tutorial search google.
Other usefull links
Hope this is helpfull.Use all these resources and do post on the forum if you could code one or not.Another thing don't try to harm any one with the virus you write as it is a punishable offence.Best of Luck