Speed correction

Many years ago I used some cassette recorder to record my parents. Recently I tried to digitalize these tapes but the cassette recorder which I used to this end was clerly slower than the old one, what resulted in much lower frequency of the voices.
I tried to make some digital pitch corrections but apparently it is quite tricky busines… Do anybody can suggest some freeware/shareware soft, which can help in an easy (but efficient) correction of this slow down effect?
Thanks in advance

well - the correction requires resampling the audio, and the quality sort of diminishes a bit. Using Nero Wave Editor (comes with Nero) you can do it, but it’s not exactly professional. Only professional software can achieve good quality.