Hi all. I was able to acquire a Compaq pentium 3 733 Mhz machine from workfor very little $. It came with no ram or hard drive. I installed ram and hard drive (Windows) '98) from my old P2 machine. When I booted up, the following message appeared. "Invalid system disc. Replace the disc, and press any key". What's wrong? Why won't the P3 read my existing hard drive? Thanks in advance.