Hi, I've found a number of websites that have loads of free samples on them.
Cyberworm's sample blog has loads of classic synth sounds
waveformless is very good too
Many are 24bit but can easily be converted to 16bit in Audacity (free sound editing software) You can import audio to allow batch conversion rather than opening individual samples. my laptop is fairly standard and easily handles 40 or so at a time.
My favourite site at present is bedroom producers blog
This has samples and vsti synths - you can download something like tobybears minihost which can host a single vsti and record the output to wav. It seems easier to record a longer wav and then split it in audacity rather than record individual notes.
If you have a daw this is probably an unnecessary step as you'll load the vsti direct but it's a quick and easy way to play with and record synth sounds and to be honest i find caustic much easier and quicker for recording ideas