hi i am a revert/convert.
past windows user.used to all the tricks and trades. i would be greatful if some of the following questions could be answered

1>does linux need a antivirus? (i heard it doesnt as most viruses and spyware are written for windows and linux ones are rare)

2>does linux have registries or anything of sort were applications that are uninstalled still left..or are they removed completely

3>does linux partitions need to be defraged..or are the filesystem made in which they dont need to be

basically i would like to know the routine maintenance of running linux

1. Not generally. The only antivirus I've ever run on Linux were on file/e-mail servers to protect the Windows clients. There are a few Linux viruses, but they are mostly experimental.

2. Applications usually store config data in /etc. If an uninstaller is written correctlym it should clean up everything. There is no registry like Windows.

3. Linux partitions don't get fragmented (they defragment themselves automatically).

this sounds to good to be true. what is the catch
so basically i dont need to do no maintenance on my ubuntu system. LOL besides upgrade to next release cycles every 4-6 months

The "catch" is that you'll have to re-learn things that you thought you already knew. Linux is not the same as Windows in many respects. In fact, it is far from it. This simple fact discourages many from sticking with Linux, although personally I believe that the benefits of learning how to use Linux properly outweigh any of the problems you may experience.