Files still partly hidden after virus removal

I have to regularly use my flash drive between my laptop and computers connected to printer at work and every time I do this my USB gets the same viruses. Nothing I can do about that, my bosses are not willing to shed money on an antivirus program. At least one of them hides files. Avast in my laptop flags and removes, or seems to at least, the viruses as soon as I try to open a file, though unfortunately I cannot remember what virus/viruses and its variants Avast detects. I have run thorough virus check with Avast fairly regularly recently as well as checking my flash drive every time I put it back to my machine so whatever problem I have, is beyond Avast:

Even after virus removal the documents that the virus or viruses hide stay hidden. I have "Show hidden files set as default and I can see the files are there but when I open the properties tab the "Hidden" box is ticked and greyed out so I cannot untick it. Not only that but the name of the file starts with a wavy line and a dollar sign, as if the file is open. How can I enable the option to untick the "Hidden" box and make the files completely visible.

Also recently the MsOffice icons of my laptop changed to blank yellow ones and and after a few days Windows could not open them, until they were reassigned a default program again. I cannot think of anything that could have caused this, apart one child pressing keys at random while I was working on a document, but I don't see it likely.

*In this country most network admins don't like them anyway, because they believe most viruses are harmless and antivirus programs just slow the computers and network down... Which is probably why many servers here are boycotted, so that I have had problem of downloading perfectly legitimate program and many of my emails, without attachments, are never received.