Is malware in temp folder harmful?

[GSDog]

I just got my parents computer working after it being down for about 18 months.

I installed Kaspersky AV 2013 and did a scan, which detected the following:

Trojan-Spy.Win32.EmailGrabber.ak Deleted 12/03/2013 19:08:11 c:\documents and settings\*****\local settings\temp\

I think the actual file name of it was 49.tmp

My question is, would that Trojan have been active/harmful or is it just a temporary file? Where would it have come from?

 

[GSDog]

Thanks.

Kaspersky seems to have dealt with it and I have run MBAM and SAS to be sure.

I couldn't see anything suspicious in start up but the PC did display a rundll error every time windows booted; it was trying to launch a .dll file at start up but the file was not there. I'm wondering if an anti virus in the past had partially deleted/removed the trojan.