Windows 7 clean installation on Dell XPS 410; slow, unresponsive

I've been troubleshooting this computer for some time now. At first, I disabled RAID because of the blue screens and I found that one was bad and the second of the RAID 1 appeared fine. Well, I installed XP to ensure it would work and that was extremely slow. My client didn't have a disc to XP MCE, but instead bought Windows 7. The installation took about 12 hours and the system is often unresponsive. On resource monitor, the 2.13Ghz Conroe CPU is barely tapped and the 2GB of RAM is barely at 30%. However, the system takes forever to boot and it very often stops responding for a period of time.

I did my research and found out that this model--original specs--can handle 7 better than this. I told the client it was probably an HDD error, as it seems to hang everytime the system must access the HDD. I can't even run the Index to find out what the systems rating is.

I memtested the RAM and chkdsk the HDDs before removing the first because of its clear faults in its inability to hold an OS installation. I recently installed the 2.5.3 BIOS update, but I haven't had a chance to install a newer version of Intel Matrix Manager.

Your thoughts?

To update: The Blue Screens were not referenced further because I solved those issues. I went to get back on the system after work and I found out that the system was shut off. I booted it up and shortly after leaving the Dell screen, the computer went into: An unexpected I/O error has occurred. Error code: 0xc0e9" Given the previous, I'm left with the impression that the logical drive has failed. Seeing as I'm unable to know just how many times the computer was halted due to errors in the middle of read/writing, it should be safe to assume that this is the problem, but I'm in the middle of waiting for the client's HDD replacement. Once again, any thoughts?