how to increase idm speed?

1.Open idm and then click on option shown below.

2.Then click on connections tab,then choose default  max. connection number the default max connection number is 8.
3.Choose maximum as 16 and then click on ok button.
4.Restart your idm to take effect.

how to delete malacious files (such as autorun.inf) from usb and from your computer ?

are you fed up of some locked files or malacious files which can not be delete or can not detected by anti-virus.
don't worry i have get rid of this problem.
you have to download this given tool from google by searching.
it also helps you to delete autorun.inf permanently.
screenshots of this given tool

how to hide/unhide folders?

1.click on organize button and then click on folder and search options.

 2.click on view tab,then click on radio button show hidden files,folders.
3.click on apply and then click on ok button.