I have tested Skype with both a quality headset/mike and an ordinary Webcam mike (maybe not to ordinary - Logitech HD 1080p), and quality was quite acceptable. Both my counterpart and I found no very noticeable difference, and I didn't notice any noticeable difference with Skype when recording with Windows' Voice Recorder or Camera. Maybe you should try to uninstall and reinstall your mike, check the settings, verify if there is any setting below Skype's requirements (there should be a minimum setup somewhere required by Skype). Is your mike compatible with your Windows OS (if you are still using XP, you might find some strange things happening, specially not being able to update things like Java). I adhere to Dmitry's suggestion, ask Skype for help, they might be able to pinpoint the problem on-the-run.