In passing, I mention that there has been considerable discussion recently about DRM and PlayReady and copy-protected recordings and the ability to retain access and playability of copy-protected recordings even when having to restore a "system image" of Win7 C-partition from an earlier point in time than was the recording date of more recent copy-protected programs.
Turns out the "magic" is in a file named c:\ProgramData\Microsoft\Playready\MSPR.HDS which holds all of the encryption key data required to play back all copy-protected recordings. It has been proven experimentally that you can restore an old "system image" of Win7 C-partition, and then while rebooting to SAFE mode (in order to work without WMC being active) copy back a preserved latest version of MSPR.HDS (which was copied before restoring the old "system image", either manually in SAFE more or perhaps in your normal nightly backup involving VSS shadow copy so that MSPR.HDS can be backed up even though WMC runs 24/7 so that this file is actually OPEN and IN-USE 24/7).
And once the preserved latest MSPR.HDS is copied back replacing whatever version was restored along with the old "system image" you restored, well now all of the copy-protected programs you had access to before doing the "system image" restore they are now once again all fully accessible, even though you're running an old restored version of your Win7 C-partition.
Much discussion about this topic is currently going on
in this other thread.
Now while installing EPG123 does require re-doing the WMC "TV Signal" setup from scratch, in order that you can DECLINE the MS Guide Rovi offer and other downloaded data, and this will definitely require that in worst case you must manually recreate all of your series recordings setups (although EPG123 Client does offer a "backup" and "transfer tool" functionality to assist) after the new Schedules Direct Guide data and channel lineups are installed in WMC by EPG123, there is no reason to "reinstall WMC or Win7" just because you're exiting from Rovi and moving to EPG123/SD.
In other words there is no loss of the current MSPR.HDS, just because you are installing EPG123. Hence there will be no loss of access to your current stash of copy-protected programs. They will all still be playable even after you migrate into EPG123.
Note: I have two HTPC machines, one running with (a) 6-tuner Ceton PCIe internal tuner card and (b) 4-tuner Hauppauge QuadHD tuner card, and the other running with (a) 6-tuner Ceton ETH network tuner box and (b) 4-tuner Hauupauge QuadHD tuner card. Both HTPC's run with EPG123 (and have been for several years), and neither machine required reinstall of Windows or WMC in order to go to EPG123 when that install happened. No copy-protected content was ever lost, because (a) Win7 was never reinstalled and (b) the hardware machine remained unchanged, across the "TV Signal" setup process.