Has my computer been infected, need help.

Hi, I’ve been away and allow two people to use my computer, one of them downloaded and installed a flv player from www.download.com. Since I’ve been back I sent the program to be scanned by VirusTotal, which came back with these infections for the file:

W32/BackdoorX.DHLT
Win32.Small.guj
Backdoor/Small.gue

I have checked and the first one seems very nasty and can spread to my usb drive, yes I did plug it in before I found the infected file, the program has been uninstalled and deleted and I have been googling away but still do not know if I’m infected or what other things may have been downloaded, can anyone help me check my computer for these infections, also the two people both deny downloding the program, could my usb pen drive also be infected, thanks for your time and help. :cry2: