Minecraft Launcher Crashing?

I've been trying to play Minecraft lately as I haven't played in about a year and figured I'd go back and mess around, but when I open the launcher it slows my entire PC down to the point of crashing, and the PC won't speed back up until I open task manager and end javaw.exe.
My specs are: Nvidia GeForce GTS 450, 8GB DDR3 RAM, and an AMD FX4100 3.6GHz.
I've tried:
Updating graphics drivers, deleting.minecraft from AppData and trying to redownload it, trying different launchers and trying to play with different versions of Java (JRE6, JRE7 and the JRE8 Beta).
Any help would be appreciated, thanks guys!

Added (1). Oh, before anyone says it, I *did* try allocating more memory to Java, but that didn't work either.

Added (2). Edit 2: Another thing, Minecraft worked perfectly before I re-installed Windows, which is pretty weird. Dunno if that helps.

Added (3). @Fallobt:
Tried it all, didn't work, but thank you! I appreciate the effort:-)

Benjamin

This is an odd one. If you had mods installed previously, you need to force update Minecraft, so delete the version you want to play on in your.minecraft folder, then go to versions (then it's there)
You might have memory taken up? Delete some unwanted files
Install Optifine! That mod is brilliant, here's a review I did of it

And update Java if you haven't already, hope this helped!

Guest