i do not have an external interface so i have been plugging my guitar directly into the sound card of my computer with an adapter .
That is your problem. You need a sound card with decent drivers and you need a Hi-Z input for your guitar. I would get a sound card made for recording ASAP and not record anything until you do so.
Onboard sound chips that come with over the counter PC's are not good for recording with professional programs like Sonar. They lack the drivers, converters and hardware for recording guitar