1: Download HD Tune and under Benchmarking run a complete performance test. Please report Average data transfer for the entire test.
2: Go to Device Manager, expand IDE ATA/ATAPI Controllers. Right click the Primary IDE channel and choose to uninstall it. Reboot and let Windows reload the driver. Repeat the procedure with Secondary IDE channel.
3: Following step no. 2 run HD Tune again and report the results as you did in step no. 1.
4: Press ctr+alt+del to enter task manager. Under Performance tab look for "physical memory". Please report Total and Available.
5: Enter "My Computer", right-click drive C: and then Properties. Please report Capacity and Free Space of your hard disk (each partition, if you have more then one).
1: The advice given to post in the malware forum is a good one. However, since it can take quite sometime to clean the computer, and at the present there is no clear indication for malware, I would recommend that you run the above procedures beforehand. If not successful, post in the malware forum.
2: The computer(s) can certainly be repaired and there is no need to consider replacement.