With $2,000 I suggest that you not even think about your final computer -- but realize that that money will easily buy you at least two and probably three very good computers that with any luck should take you well into your 80s.
Assuming that you do not do serious gaming, photo editing, huge spreadsheets, or other cpu or graphics processor intensive tasks, there is no reason to spend even close to $2,000 on a machine today. (And I say that as someone who from the mid-1980s until the past year or two was a firm believer in the motto that the computer that I really want is about $2,500.) But for web access, word processing (even very serious stuff on book-length manuscripts), email, ordinary spreadsheets, ordinary photo editing, and similar sorts of things, you should be quite happy with a computer that ranges in price from $400-800 -- $1,000 absolute max.
Even if a desktop may last a bit longer -- and that is not obviously correct -- that certainly should not be a consideration. The question is what you want to work on and have in your house. It sounds like the clean simplicity of a laptop is attractive to you. So go for it.
Now you have to choose size. Your choices range for a 10 inch netbook up to a 17 inch behemoth that you will almost certainly leave fixed on a desk most of the time. The issues here really are 1) aesthetics, 2) readability/usability, and 3) the fact that the smallest boxes usually have somewhat less computing power. (I am ignoring portability and battery life, which seem not important to you.) But you will be surprised at the (pleasantly) size of hard drives on these machines. Unless you have truly immense music and photo collections, they will be adequate. And if you really do need half a terabyte or more of storage, and external drive will handle that easily and cheaply.
There are great laptops out there in the $600-800 range that blow away a five year old $2,300 machine that I have passed on to a relative who still uses it happily. And if you like the look of netbooks, for $400 how can you go wrong. (I did that six months ago, in part because I wanted portability and long battery life, and I have been very happy. But I suspect that you are probably going to be looking at 13-15 inch machines, where you do want to be in the $600-800 price range, I suspect.)
Which one. It really doesn't matter -- or, rather, there are lots of good choices. Get a good brand, from a reputable supplier, preferably when they are having a serious sale. And given that you are in Saudi Arabia, the availablity of local warranty support may actually be the single most important consideration.
Put away the rest of the money. When this one dies, do the same thing. And if you keep in the $600 range -- which is VERY doable in the US -- you can do it another time as well. Figuring five years as a reasonable average life for a computer of this quality, you should be working away on a very nice machine into your 80s for your $2,000. I assure you, though, that if you spend it all on one now by your mid-70s you will be dissatisfied.