Computer suddently slow after a blue screen

My computer was fine until I had a Blue Screen 0x0000007A.

Right after that happen, I did a full recovery backup with the Acer tool that they give with the laptop cause I wanted to reformat for a long time. Now the drivers are all up to date and Windows 7 x64 up to date.

But since the blue screen, my computer is so slow, it takes like 30 minutes to reboot. And it keeps freezing like 20 secs randomly(not the mouse, only the program stops responding).

I thought it was the RAM, but I did run memtest86 and I had no error.
What it could be? The HDD?

The weird thing is that it takes so much time to boot and that it's not slow when when it's fully started

The laptop is an Acer Aspire 8940g.

Does Windows offer to report your error a short time after you start the computer? After a BSoD, Windows collects data about the crash (hence the slowness) then offers to send it for analysis. After sending the data, Microsoft returns solutions for known problems, often in the form of a software or driver update. I have fixed numerous crash issues by using the "Report this error" feature.