main pc freezes while others write to hdd

[gallup]

My Dr. asked me about his billing program on a network giving him a problem. ntwk pc #3 is writing a large file to the hdd of pc #1 at his front desk that uses the same program to schedule appointments. Software co. says it is the pc that is the problem. Can't do anything with pc#1 for quite a while until files are all written to hdd from pc#3. pc1 is p4 2.4ghz with
1gig ram. Uncertain if it is just this program that freezes up as that is all they use on this pc#1. It is the main pc and is not on the internet.
Does this sound like a hdd slowing down the pc as files are written? Just too much for the processor to handle?
What are some possible solutions? second hdd on pc1? faster dual core pc?
A server solution? (that sounds very expensive though and is it really needed?). Is is a memory problem perhaps.
Input is greatly appreciated.
don't even know if this is posted in the right forum.

[johnwill]

Sounds like the hard disk is running in PIO mode, not DMA mode.

Start, Run, devmgmt.msc

Expand IDE ATA/ATAPI controllers.

Right click on Primary IDE Channel and select Properties.

Tell me what appears in the Current Transfer Mode: slot for each of the two channels.

[gallup]

primary is on ultra dma mode 5 and secondary is on ultra dma mode 2

seems as though this freezes up while other files are saved until save is complete then works fine again.
problem occurs when this being a Dr. office and they have a patient file open to bill or schedule, they have to wait for large file to finish saving before program use can resume.

anything else and thanks,
Mike

[johnwill]

Try copying a large file between workstations and see if it's just this application that causes the issue or any file sharing.