My pendrive gives the error"the disk is write-protected"what to do?

[baibav kumar]

recently i inserted my pendrive in my friends laptop which had many virus in it and after that even i cleaned them all but the problem started with it that whenever i use it i gives the error "the disk is write protected" and i then after thai i can neither remove or add any thing to it & i have to remove ,re-insert and format it without opening it.
it dosent occurs always and as soon as i insert it but it occurs when i am working with it my avast free antivirus is uptodate yet it dosent detects any virus.