Please help! my lightroom 5 crashed and i had to put country and serial number again. I then re-opened lightroom and it contains nothing, no presets and no imported/edited photos. I also can't find the catalog it seems as if it was overwritten
A crash won't have deleted your catalog. What COULD have happened, is Lightroom's preferences became corrupted, so Lightroom forgot where to find your catalog and the 'store presets with catalog' setting. Search your hard drive for *.lrcat files to find your catalog.