I would say that your CPU is adequate. IIRC, PrE 4 had a minimum of 2GHz (could be +/- a bit).
Now, "Memory" is twofold:
Windows Virtual Memory (Page File)
If you are getting Memory errors, I'd first download a RAM test utility, but usually the physical RAM does not go bad - still, it has been known to happen. Next, I'd look closely at my Virtual Memory in Windows. I am a big fan of setting this to static @ ~ 2.5x my physical Ram, and locating it on my fastest HDD. Most systems will run fine, with it located on the C:\, but if one also has their media and Projects on that drive, then an additional HDD might free things up a bit.
Then, I would look at what else is using my RAM and my Virtual Memory. Most computers have tons of totally unnecessary programs and Processes that steal Memory. This ARTICLE will give you tips on cleaning out many of these, and then setting up one's computer for an NLE session.
This most often happens because of lack of scratch disk space on your C drive. Even if you have plenty of room on your C drive, the program needs CONTIGUOUS space -- so it can have problems if your disc is not clean and defragmented or if your drive has errors on it.
Here's my regular maintenance regimen. Advanced System Care is free from IOBit and it will clear off you spyware, temp files and clean up your registry. This and defragmenting should help tremendously.
You should also ensure you have the latest version of Quicktime.