My computer's system alert keeps tell me I have a Trojan yet none of the antivirus software I h

that happens because those system alerts are fake. it's a small spyware program which forces you to buy some stuff or just keeps blinking and makes you mad. and as it's spyware and not virus, antiviruses can't and won't pick it up. what you need is antispyware., try spyware doctor, it worked for me when i had the same problem.

you can download it here:

http://www.2-spyware.com/review-spyware-...

My computer's system alert keeps tell me I have a Trojan yet none of the antivirus software I have detects ithhijack this

go to www.savemybutt.com and download avg, if u have a trojan this will pick it up

My computer's system alert keeps tell me I have a Trojan yet none of the antivirus software I have detects ithliveupdate

if you have norton or mcafee, should be able to find, other may not...

try adaware or spy bot instead of antivirus,

http://www.snapfiles.com/Freeware/securi...

if needed, run in safe mode,

empty temp folder,

empty browser cache files..

..
I would suggest you to do an online scan from www.pandasoftware.com/activescan and see what does it says. Also download an antispyware like Ewido and do a full system scan. Chances are there that your antivirus is not able to find it or that program which is saying that your system has a virus itself have been infected.
A trojan isn't a virus, it is spyware and AV programs can't find or eliminate it. Get Ad-Aware and SpyBot, both free from download.com, install and run them. they will find the spyware and get rid of it.