list the brand and model of the speaker(s). unless you do we can only offer generalized advice.
does your speaker have its own power cord or not?
if it doesnt have a power cord then your pc might not be able to connect direct. unpowered pc speakers are normally 2-5w or so. pc speakers which are 10w typically have ac plugs. without a plug you will likely need a really cheap amplifier.
if it does have its own power plug then i wouldnt see a problem.