lol, windows rot :-), I have an XP system that has been on the same install for 11 years now, with 150+ programs. It is faster today than the day it was installed. Just have to chip off all the rotting and useless stuff, keeping the fresh meat going stronger.
Windows 7 differs in that things are harder to remove, the registry is more bloated and harder to delete things. There is all the extra compatibility there, and being added , especially in 64bit version. More MUI , tracing and logging, more bloated programs that we buy and install. The same older stuff from before, now with more bloation and filled with features. More dependencies in all ways, both the systems and the programs. If you got rot before, you got more rot now.
Many thing go in, and do not come back out, if I can get 300 pages of space and 2 weeks I will show you some of them :-) but you will just want the summary. And quick fix removals all have ramifications, so there is no script or program that could possibly address everyones specific junkpiles.
SSDs start slowing down the more full and mixed up they are, depending on the size of the SSD, windows 7, I could GUESS that the rot factor would be at least doubled, relative to the original install and speeds. (uhh mostly due to the system and the user junk)
All of which could could be changed by doing maintenance , maintenance that is harder than fresh installs, and that is getting harder and harder to do at all. SSDs have maintenance routines also.
SSD slowdowns on modern 2011 drives are . .. About like that (Minor) win7 supports trim and therfore DOES the maintance.
Hard drives get to ~1/2 speed when the slower parts of the platters are used, But this is about the OS, so partitioning the system at the front end of the hard drive would keep that aspect of it completely out of the picture, leaving just the fragmentation, which Again win7 maintenance with a defragmentation routine.
Relative- The SSD is so fast, if the whole system was a complete mess, there was no maintance, no trim, not garbage collection, the SSD speeds could keep the system going awesomly. But will that make the system not slow down with trash? I/O has costs beyond any one items speeds. Relative to when it was first installed and everything was going wonderfull, there are thousands of reports of the system becomming a dog - Relative.
Benchmark the same system, that a user claims is "suffering from windows rot" , is the cpu slower? noo, gee did the GPU start loosing transisters :-) , do the drives all test out as operational and about as fast as before, when there is nice clean spaces to write to , yes. So gee, what could have possibly happened , Magic :-) Just apply some re-install vodo, and everything you personalised, and set up , and installed will be tossed out with the dirty bathwater.
What has happened is much thicker and more complex and often has to do with many aspects of the system, it isn't just programs, it isn't just leftovers, it isn't just drivers, it isn't just running things, it isn't just the registry. it usually is everything, adding in its own complexities and very minor things on thier own, that compound.
I maintain that there is no such thing as windows rot, give me 8 more years , and beating the system to death and tossing out tens of thousands of registry entries, disabling services, and chucking drivers I don't use, and I will prove it :-) in the meantime keep your re-install disk handy :-)
Better , Make a clone image of the fully operational system that you really like, and retract back to it instead.