[s83]

I have a hp 520c. Weeks ago while on-line it errored and said it would shut down and did. Re-boot took 45 minutes. Machine ran so slowly it was unbearable. Took it to hp service center. They said hard drive was shot. I replaced the hard drive and attempted to run system recovery disks. Took over 8 hours to install. At finish re-boot was no different. Still down. No system software can find a problem. Switched memory sticks dimm1 & dimm2 to se if maybe 1 was bad. No change. I'm running system recovery again now. What could cause this failure? What am I missing?
Help:

 

[s83]

clintfan

Ok, I replaced the hard drive my self. Connected it just how the old one was. We did run scandisk on it first and it did fix a few errors but didn't fix anything. The old drive is still in the machine but I didn't hook it up yet. New drive is hooked to ribbon marked "Master" and power is hooked to "P4". I assume to connect "Slave" and "P5" to old drive but will not until I solve present issues. When I switched memory the machine ran setup disks in a fraction of the time it had before. At the end system recovery goes to copy files. I started this at 11 PM Sat. Its 12:20 pm Sun. and files are only to 26%. Not good. Office Max has 256 memory for $10 after rebates etc. Shoul I replace both? Could this be it? I've tried to watch memory count up at boot but this machine starts monitor to slowly. Thanks for your reply.