Not much to go on such as what operating system are you using?
If you are using windows xp do this:
Browse to C:\Program Files\Windows Media Player
Double Click setup_wm
That will re-install Media Player
Media Player is usually damaged by trojans or spyware.Feel free to download HijackThis and post a log.
If you cannot reach either site it is available from my signature.You need to put HijackThis into its own folder. It makes backups and they need to be kept all in one place.
Click My Computer, then C:\
In the menu bar, File->New->Folder.
That will create a folder named New Folder, which you can rename to "HJT". Now you have C:\HJT\ folder. Put your hijackthis.exe there.
Current systems: WHAT OS, BackTrack-raw, PCLinuxOS, Peppermint OS 6, Kali Linux
and a custom Linux From Scratch server hosting a bunch of top secret stuff.