Assuming that there is some unknown issue with thumbnails, what about disabling thumbnails? It's a dirty workaround but may save the day.
On the default "save/load/whatever a file small Win 7" window there is a icon to the left of the help icon (blue dot). If you click on the small black triangle to the right of it, a bar with various options appears, choose "details" or something similar and never see the thumbnails from that screen again.
"It won't be anything in the startup as the memory is okay after booting the PC and it works just fine as long as I don't work with big files or transferring a lot of files. I.e. I don't have to use Photoshop to get cache issues. Transfering files from one drive to another gives the same issues."
Hmmm, this is pretty obvious signal that there is an issue in handling mass storage devices, the above workaround isn't going to fix that. Bad drivers
, wrong BIOS settings, or maybe even faulty HDD/parts.
Which explains why an Acer was outperforming a Lenovo.
To see if it is bad drivers you must go to the Device manager and look at the HDDs, if the name of the disk is something generic and not a bunch of letters and numbers with a manufacturer name, then you may have driver
issues. It would be that Windows 7 uses its generic drivers so the HDD is kinda usable, but won't work very well because it wants its own drivers.
As for bios settings I always had to "spray and pray" so to speak. Alter a setting that you think may have something to do about HDDs (usually they are kept together), and see how it runs after booting Windows 7.
Of course I don't think you should do that (my guesses are more educated than yours as I have more experience
). You can ruin it if you don't have some experience in fixing computers.
If it's a faulty HDD then check it with crystalMark or whatever other disk-testing software you like.
Ps: I add this as a sidenote because I really don't think it's the case for a Lenovo lappy, I had in my hands a couple desktops with the same issues and it was due to the motherboard's ATA speed being 1.5 Gbit while the HDD speed was 3 Gbit. Jumper on the HDD set correctly and it dialed down the speed to 1.5 Gbit, problem solved.