Why AIDS is not curable?

what is the main reason for AIDS ? and why is it not curable?
and what are the resent drugs for AIDS

it is a virus. It works by converting the serum to infection in the blood. The anti - viral drugs used to treat it are sophisticated and good, and expensive. They work well, and th epatient has regular blood tests to see how their white cells and blood is responding to the drug. To work 100 per cent, these drugs would have to change ALL the body's' blood serum normal, eradicating all the HIV infection. This was done; a newly diagnosed HIV + young American man did test negative after a course of treatment - but the treatment made him very ill indeed. It is unlikely it will happen on a wide-scale.
The modern drugs are good; they will give the patient many healthy years they would not normally have. I have friends who are HIV + and paying into pension plans. They may well live to need them. But it is an illness and you have to work hard to keep your mind and body healthy

Its not curable because the virus changes to rapidly for us to make a vaccine that would be affective.

Aids is a virus that inserts its own DNA into your cells, giving its own instructions. You cant kill the foreign DNA without killing your body's cells.

HIV most likely came to us through the bushmeat trade. Other primates, such as the chimpanzee, have similar viruses and may have acted as a carriers(chimps and other primates do not succomb to the disease).
Unfortunately, the virus mutates in our bodies so often and so radically that it's like the body encountering a new bug every time it does so. Additionally, it hides inside our t-lymphocytes(type of immune cell); it's difficult to fight something that hides within your primary weapon against it.
The drugs used to treat it are mainly anti-retrovirals(HIV is a retrovirus, a class of viruses). I am not a doctor, though, and forget their names.

The current held belief (although some arguments have been made against it) is that AIDS is caused by a virus called HIV (Human Immunodeficiency Virus.) This virus infects cells of your immune system, in particular Helper T cells. When you get any sort of infection, the helper T cells are important for 'rounding up the troops' of your immune system. They help all the other important cells to get activated so they can do their job. One of the reasons why AIDS isn't curable is because it infects and harms the cells that you need to fight back against a viral infection. With HIV, you gradually lose one of the key 'Directors' of the immune system.
Another important thing about HIV is it's a retrovirus, meaning that through some nifty copying of RNA and DNA, it turns it's RNA genome into DNA, and then splices it directly into the DNA of the infected T cell. So you cannot get rid of HIV because it is hiding out in the DNA of your own T cells. Like others mentioned, it also mutates rapidly, making it difficult to find long-term drugs, and develop vaccines.
Therapeutically, it is also difficult to get rid of because it spends most of its time within these cells, and not running around within the blood (at least early during infection). Current drugs to treat HIV focus on blocking the virus's replication cycle, such as Protease inhibits (block the main protein-building enzyme of the virus), Fusion inhibitors (block the virus from infecting the T cells), and other drugs which mimic DNA molecules, but are different enough that the virus cannot continue replicating.
I hope this helps, and it is easy enough to understand. Below is a link to the world health organization. They have a number of articles. You can also check out the CDC (Center for Disease Control) website for your area.

The above answers are very good but for a bit more information on viruses in general we have never been able to cure a virus. Once you have contracted anytype of virus you have it. Now, we have been able to create vaccinnes where if you don't have it and come into contact with a virus you will not contract it but never a cure. We also have never had DVD players before so anything can happen. The real issue is why don't we have a vaccinne yet? The horrifying reality is that drug companies are making SOO much money keeping people alive that have AIDS that it is not profitable to either find a cure or a vaccinne. This sounds deplorable but if you investigate into the facts a bit I think you will find this very likely could be the case. And by the way the REALLY sad part is is that if everyone would have protected sex until the last AIDS case has ended there would be no more AIDS. It only exists because we keep infecting one another!!!! Yep--AIDS could be a thing of the past if everyone would just get checked and wear a rubber. So, in reality--WE are the cure. I hope you rememebr that when the time comes. In the immortal words of Madonna-"Hey you--don't be silly--Put a rubber on your willy!!"

HIV lies dormant in T-Cells that arnt active. The HIV combo at one time was once thought to eradicate HIV from the body. It nearly does. Once those T-Cells become activated they begin producing more HIV virus instead of doing what they are supposed to do.