Downloader.Gida.a

My Network:
Inspiron 1521/w. Vista Home Prem
Dimension 2400/w. XP Home
Zyxel 330W router

Greetings,
I need to ask a quick question which I hope has a quick answer, How can I know that I have nipped Downloader.Gida.a in the bud, before it has had a chance to more throughly infect my system (I have a network with two computers)? Yesterday, I got an email from a friend in Mexico (he writes in Spanish, I write in English! We miss a lot in translation). The long/short of it is his email contained one of those bots that pretend to be scanning your hard drive and finding 1000s of "errors". I stupedly clicked on a link to a postcard he was sending me. Immediately, it started scanning my HD. I stopped it short but it did do enough scanning that it showed me a representation of my HD. I ran AVG Virus Scan, and AVG Anti-Spyware, and only the Anti-Spyware picked up the Downloader.Gida.a, which I understand is a backdoor trojan - ??? Isn't this a virus, rather than a spyware? Why didn't the virus prog find it?

AVG A-S said it could only quarantine it, and showed only one trace of it. What I need to know is whether we got it early enough or can I expect more problems? And if we didn't get it all, how can I proceed?

I am researching and cleaning both my machines as fast as I can, but my sense is that if I state the specifics here, there may be a more specific remedy for correction.

I thank all who can contribute to this question.
john

 

I was unaware that seeking assistance from multiple sites was considered poor net etiquette. My apologies.
john

 

Chas,
I think I'll cut my losses and lug my unit down to my local computer shop, and let them have all the fun.

Thanks for your responses.
john