I have a computer that was running XP Home addition and had a hard disk failure.  It is a pentium 4 with 384MB of Ram.  I have replaced the hard disk with an 80GB IDE hard disk.  My problem is that it will not load XP Home Addition.  It will go through the initial load and then fail to load some EXE and DLL files.  It had just 256MB of RAM initially and I added 128MB more thinking it was a RAM Memory problem.  I then loaded Windows 98 and then did the upgrade to XP Home.  It loaded after a few qliches but still has many problems on running such as it will not read a DVD disk that I know is good.  Any suggestions will be greatly appreciated.
tetonkenYou formmatted the new HDD and installed a fresh installation of Windows on it?Have you re-installed your motherboard drivers ? ?
When you say it won't read dvd's what program are you using when this happens ? ?
Are you sure the RAM you added is correct for that machine ? ?I diid a new NTFS partition and tryed to load XP from scratch and it failed.  So then I did a Fat32 partition and loaded WIN98 and did the upgrade.  The DVD that it won't read is a backup of pictures and documents.  The DVD has almost max capacity of data on it.   
The Ram I added is DDR 333 same speed as the RAM in the machine and it seemed to recognize it with no problem.  I put the RAM I added in the first slot and I got further with the XP load than I had with just the 256MB of RAM.The machine is about 4 years old and there was no disks for the mother board.   
kenSome of this issues are caused by CD-ROM or DVD-ROM or any scratch on the disk that leads to led not to pick up some data on the disk.

Through experiance i had the same problem for a month tried different disks just then to figure it out it was rom read speed was too slow to pick up some DLL files..

Ok WHATS the speed on you Rom drive and how old is the disk you BOOTING from?
I am not sure of the speed of the DVD but I would think it is at least a 12X.  The disk if fine, it is the backup of her pictures and Documents.   The main problem is not getting a clean load on XP.  I am fairly sure it isn't a motherboard problem and I think I have rulled out that it isn't a RAM problem. So now I'm really STUCK as to where to go next.
Ken