Laptop question?

2 years ago, i bought a HP. within a year, it needed a new head drive but was still under warranty so i sent it in and it was repaired. 6 months later i'm typing a computer for a long time and same thing happens but not under repair. now a year later, hp has finally let me put it under full warranty, for $120. i bought a new computer which works fine and wanna give this one to my sister, who asked for it. question is is it better to just get it repaired and keep it or get it repaired and sell it? is it ethical to sell it? and is it right if i ask my sister to pay for at least some of it bc she wanted it?

Laptop question?free anti virus

Give it to your sister, ask her to repair and let her use. If you sell outside, it's a scrap value.

Laptop question?internet security software

Knowingly selling it broken in my opinion would be wrong. Did you mean hard drive instead of "head drive"? If so, a hard drive crashing does not mean the computer is defective. A couple months ago I had to replace a HD 3 times before I got one to work because they all had the "click of death" break, which is caused by a defective build at the factory. I would think your problem lies in whoever made the HD, and not the laptop.

Hope this helps!
First of all, maybe you should use a Dell next time(NOT ACER). Secondly, it is ethical to sell a computer with issues, you just have to make sure that the buyer understands that the computer doesn't work properly. Also, if you only have you and your sister that use computers, you should probably sell the other (unless you need serious privacy). Besides, its easier to keep one computer protected, firewalled, etc. than two.
Just give it to her with warning that it needs repair.
you cannot sell it if it is broken. and it is your sister. fix it then give it to her. thats what family is for :)