BSOD+Install errors help!

[Shadeaces]

A computer i built 6 months ago is now recieving many errors.
1) I recieved a blue screen and had errors popping up when installing programs.
2) I reinstalled windows and many .dlls were missing, when i finally installed it without error i could not install programs without getting errors.
3) I tried repairing and it still did not improve

Next i replaced the hard drive-
1) I tried steps 2 and 3 again but it still did not work.
2) I ran memtest86 and every item fails the test, the comp boots up but its still having blue screen and errors.
3) I tried resetting the cmos and still same problem.

What should i do? What component is failing?

Thanks

[glc]

I ran memtest86 and every item fails the test

Think about this for a minute. What does memtest86 test?

[Shadeaces]

im guessing its the ram, but if there were ram problems it wouldnt boot? Could it be a mobo issue as wel?

[flanzig1]

Ram going bad can cause problems from the PC not starting to intermitent freezing. If you have more than 1 stick of ram, try one stick at a time to see if the PC is stable and test each stick with Memtest by itself.

[LeftyAce]

Dying ram can still boot, but will exhibit instability like you're seeing. What ram, processor and motherboard do you have? I'm pretty sure you need to replace the ram...
*edit* DO try flanzig's suggestion first.

[doubledragon5]

If your ram fails the memtest than it is the ram causing your problems.. Do as suggested and test on stick at a time with memtest if you have more than one.. If they both fail than that is your problem time for new ram...