unzip the items to your 'content' folder ( c dazstudiocontent ) using either windows built in zip/unzip app or a 3rd party one like 7Zip(free) once they are extracted to the content folder you must see if they are Poser files (.cr2, .pz2, .pp2, .fc2, .hr2, and textures) and that they are in the correct folders in libraries. .obj files should go into the 'geometries' folder.
D/S files (.ds, .dsb) usually reside outside the 'runtime' folder. you should make a folder for the .jpg(textures) files outside the runtime as well, some may have to be put there for D/S to recognise them.

99.9999999999% of bought content will sort it self into the right folders, but some freebies are not so tidy, so it pays to check after extracting them.
IMPORTANT :- move files around BEFORE doing a content search otherwise the files may not be accessible after.

btw you access the extracting apps by right clicking on the zip file, they or it should be in the drop down menu.

one last point, it pays to install D/S somewhere other than cprograms because Vista is funny about having D/S installed there and may not work very well. you could install it  somewhere like
c Daz Studio
hope this helps