Well, if you "can't log onto it" to download, what's the point in asking for websites to download testing tools? Anyway, here are two tools:
Memtest86 - A Stand-alone Memory Diagnostic
HD Tach is a physical performance hard drive test.
Did you build this system, or install the processor yourself? Has it run OK in the past? How many fans are installed? Can you get temperature readings?
I wanted to buy the product and run it; not download it. In regards to your other question, I didn't build the system. From what I was told, it used to work and then it started freezing. When I opened the PC, I saw one fan and I can't get any temperature readings.