I have just started using Comodo antivirus software and it has detected TrojWare.BAT,DelTree@<hidden> Just want to know if it is a bad one. What is the risk level and what does it do. I don't know how long it has been in my computer. My Norton, Windows Defender and Spybot have not picked it up.

I did a search for that "TrojWare.BAT,DelTree@<hidden>", there a loads of pages on Comodo forums and other sites about people getting that same Trojan and variations of it. I went to the knowledge base on Comodo, and they have no record of it. That file is most likely a false positive. When an antivirus scanner reports a file as being infected, when in fact it is not, that reporting is considered a false positive.

Try a good online Scanner and see if that so called "TrojWare.BAT,DelTree@<hidden>" gets detected:

http://www.kaspersky.com/virusscanner

or

http://www.pandasecurity.com/activescan/index/