Just got through with scanning and I'm pretty sure the viruses found are false positives

Here are the results:

C:\Users\Janelle\Downloads\winrar-x64-392b1.exe: Trojan.Agent-145791 FOUND
C:\Windows\Downloaded Installations\BE32C101-A55A-4DC3-BE29-CB56338B18CA\ATMinInstall.msi: Trojan.Dropper-21083 FOUND
C:\Windows\Installer\2dea1.msi: Trojan.Dropper-21083 FOUND
----------- SCAN SUMMARY -----------
Known viruses: 734146
Engine version: 0.95.3
Scanned directories: 41305
Scanned files: 196244
Infected files: 6

Not copied: 3
Data scanned: 38779.63 MB
Data read: 32032.14 MB (ratio 1.21:1)
Time: 13836.525 sec (230 m 36 s)



Also Every time I go and click on the save report button, I get this message: "Common dialog failed with error code ffff"

I got basically the same message:

C:\Windows\Downloaded Installations\{1E5C8663-E912-4E26-8999-B04AED31567A}\ATMinInstall.msi: Trojan.Dropper-21083 FOUND
C:\Windows\Installer\2b778.msi: Trojan.Dropper-21083 FOUND

----------- SCAN SUMMARY -----------
Known viruses: 753562
Engine version: 0.95.3
Scanned directories: 30044
Scanned files: 179439
Infected files: 2
Data scanned: 76380.76 MB
Data read: 123794.63 MB (ratio 0.62:1)
Time: 23568.310 sec (392 m 48 s)

I didn't have any problems saving the scan report.

So are these false positives?
I'm running Vista and the machine has become slower, Firefox is acting up sometimes too (windows won't close or minimize).
Thus I've been worried about a virus or something causing this. Would be nice to know that this is not the reason at least.
Windows Defender says that I have no malware "on board". So either it is a false positive, or it is a virus that is not recognized by Windows Defender.

Hope somebody can answer and clarify this!
Thanks in advance.