May be able to offer some advice here as I went through a mega jarre phase about a year ago lol. For drums you need korg minipops 7, best vst for that is the superwave tinipops drum machine which has all the same sounds (and even some midi files to replicate some jarre tracks directly) If you want to go down a free route, look for some minipops 7 sample packs (google it) as their may be a few about. Strings on the oxygene period tracks were mainly provided by the eminent string machine, again there are a several vsts that emulate this, gforce string machine being one, any of the superwave performer or profession synth vsts (they all have jarre patches) Cakewalk z3ta has a great oxygene patch which is an exact recreation of the oxygene famous lead line. Native Instruments reactor has a stunning recreation of the eminent string machine with loads of oxygene patches I've used loads and also the awesome small-stone phaser effect which is essential for jarre strings called Eminent-V 310 Strings Ensemble, this is the best jarre string recreation ever. There is loads of info if you google it as Jarre has encouraged people to make their own version of the oxygene album track and there is a great deal of stuff out their to read with guides and things, just go searchin
