The key thing is not to transfer any executable files, or anything which can contain executable parts (ms office documents can contain macros which are executable and can carry viruses), or anything which could exploit the program used to open it and hence execute itself.
For ordinary transfers between machines your safest method might be to first use the antivirus on the first computer to scan the files, then upload the files into google drive (using the web browser interface, not using the "drive for pc" program) which itself scans them upon upload, then log out of gmail, and open gmail on the other computer, then download the files (google drive scans them again during download), then scan them on the second machine with your antivirus and with a second opinion scanner like malwarebytes. If the file is not at all private then you could also upload it to virustotal for some 50 more or so opinions, but only if the file is not prvate, because files scanned by virustotal are uploaded to their servers and (I think) kept on them forever and (maybe) accessible to others. The key thing to do is make sure to scan the file as many times as possible, with as many different scannign engines as possible. Also make sure to check it for double file extensions, these can be used to pretend a virus is a picture or a pdf ( something like imonlyaharmlesspicture.jpg.exe is not a harmless jpg picture, it's an executable exe which, given the file's creator chose to try and hide the fact it is executable, is probably a virus). This can be done by unticking the "hide extensions for known file types" option within "folder options" in windows' file explorer.
But transferring from an infected machine is not so simple, if the machine is infected it is best to assume the infection can do anything (including magically turning normallt safe file types you try to transfer between machines into executable nasties) and get the infection cured.
It might be wise to copy the files you need from the infected machine onto a CHEAP usb drive or dvd-rw or cd-rw disc now, incase the cleaning up of the infection ends up needing a reinstall of the OS, but if you can cure the infection (starting a thread in the virus removal section would help you with this) expect to snap this cd/dvd in half or dump this usb in the bin, under a rotting pile of vegetables once you are finished cleaning the infection. Such a copy is a last ditch attempt to save the files, incase a cleanup is not possible or incase the virus does more damage than it already has, or incase cleaning up requires reinstalling, if the infection can be cleaned up you destroy the potnetially infected media, if it can't then atleast the files are not toally lost. You wouldn't want to get the infection back by plugging that drive into anything.
Edited by rp88, 04 August 2015 - 04:35 PM.
Back on this site, for a while anyway, been so busy the last year.
My systems:2 laptops, intel i3 processors, windows 8.1 installed on the hard-drive and linux mint 17.3 MATE installed to USB