oscillascope help

hi all,i have downloaded a program that turns the pc into a oscillascope turning analogue signals to digital using the pc's soundcard to digitize any input waveform (speech, music, electric signal, etc.)are these programs any good and where could i buy the probes so i could check the outputs of any circuits i build?.thanks.

Keep in mind that the frequency range of a sound card is limited and that within that range it may not offer a uniform response across the band. You might want to check your final arrangement against known inputs.

also, aren't there capacitors in there that will block any DC input? So you will only be able to measure AC type signals?