The trial has all features enabled, so your problem is not caused by the fact that you are on the try out period.
Have you tried any other means of getting sound in from the mic input - for example, a standard pc microphone (or microphone/headset) with Skype or a similar Internet telephone program?
You may have the mic input disabled in the Windows audio options. On XP (you didn't mention what OS you have) you can find the recording mixer in Windows Control Panel > Sound and Audio Devices > Audio (tab) > Sound Recording > Volume...
How do you connect the turntable? Are you aware that you can't connect a turntable with a magnetic cartridge directly without a phono preamp? (Some turntables have a built-in preamp/RIAA correction module and naturally you can use the standard tape out connectors on your stereo amp/receiver.)
Another issue is the quality of the internal audio devices on laptops. Quite often the mic in connector is only mono and not of high quality. For serious recording I would recommend an external USB audio interface - for example, this model:
http://www.rolandus.com/products/productdetails.aspx?ObjectId=743&ParentId=104. It is relatively inexpensive, has stereo RCA in & out connectors and provides high quality sound.