Most lossless DRM removal techniques require that you have the original license to play the material (ie: you actually bought/paid for the content). They then circumvent the DRM mechanism to dump the decrypted material (using your license) into a DRM-free file, without re-encoding (original quality).
For WMV, the most popular DRM removal program was FairUse4WM.
However it requires that you use an older version of Windows Media Player (with an older DRM version which can be bypassed). Some content providers have wised up to this and updated their DRM, requiring you to upgrade WMP in order to obtain the license, thus preventing you from being able to use FairUse4WM.
The other method is to use a re-encoding program, as suggested above.