Thomas is really is far too modest to boast, so I will so it for him.
I recently paid far too much on eBay for a 42s. The collector part of me is glad to have it, but I don't use it much for any RPN programming of substance. For this, I am positively crazy about Free42, which I find runs very well on the larger screen of a PalmTX. Thomas has given us a simulator, not an emulator, and as such it is very fast and accesses available RAM on the handheld device for program and variable storage. Shift CATALOG MEM routinely tells me I have about 4.5MB or more available for storage, vs. 6.9KB max on the actual calculator. Plus, Thomas's implementation of Hugh Steers' BCD20 floating point package provides 25-digit internal precision with the transcentental functions computed to at least 20+ digits of accuracy--more guard digits than anyone could reasonable want in a handheld scientific calculator. It is also free (though I would recommend coughing up the 30 bucks to support ongoing development), and the developer is obsessive about responding quickly to bug reports and is overall a simply super nice guy.
PDAs, emulators, and simulators are not for everyone but if you are open to the possibility I would take Thomas' advice--back up your existing 42s programs and convert them to *.raw (though I must admit I am not familiar with perl so I haven't been too bold about using txt2raw myself). That way, if your 42s continuous memory gets lost at least you will be able to run your programs under Free42 on any of the several platforms it supports.
As you can tell, I am a vigourous proponent of Free42. At least until Mr. Smith comes out with the proposed PalmOS version of nonpareil, Free42 is by far the most satisfying HP calculator emulation/simulation experience I have ever had in handheld form.
Good luck!
Les