BT Homehub 5, 2XPC connected, one slow other normal, why?

Good day to all, I am hoping that someone can lead me by the nose with help with the problem I shall now outline. I am reasonably proficient with general PC subjects, having built my own PC. However, the ins and outs of the technicalities concerning broadband subjects are a total mystery to me.
I have two PC's, the main one is runnung Windows7 Professional 64bit and the other is running Windows 7 Home premium 32 bit. They both connect to a BT Homehub 5 router and thence to my ISP, which is BT.
Current download speeds are consistent 75Mb download and 19Mb upload on the 64bit PC.
Current download speeds are consistently variable from anwhere between 23 and 75Mb download and 2 to 9 Mb upload on the 32bitPC. The 32bit machine always has trouble connecting and as I am a complete numpty in these matters, am at a loss as to what to change to improve this situation.
Sorry about the verbosity good people, but I hope someone can assist me.

How are the 2 PCs connecting to the HH5?

Thanks for the reply. Both PC's wired. Ishould add that I have BT infinity 2 unlimited access, if that helps.

Edited by deleted (Fri 14-Nov-14 17:19:21)

Have you tried swapping the wires?

Yes I have, even although I installed brand new ethernet cables to both PC' swhen first receiving the BT package. The ADSL cable to the new master socket is also new and a BtTengineer installed and checked all of their system.

What are the hardware specs for the two machines, including the network adapters?

Windows Pro 64bit:
CPU: AMD FX630, 3.5Ghz X6 cores
Mainboard: Gigabyte 970A-DS3P
Memory: 16Gb crucial DDR3, 669Mhz dual Channel, unbuffered.
Graphics: Radeon R7-200series, 2Gb onboard RAM 30 MHz
Drives: Seagate ST500, 450 Gb (Primary drive)
Toshiba DT01ACA200, 2Tb.
DVD: 2X CDDVDW SH224DB ATA.
Audio: Onboard realtek Hi Def.
Network adaptor: Realtek PCIe GBE Family controller.
I shall follow shortly with the 32bit spec.
thanks for your time.
James.

32bit
WinHome Premium SP1
CPU: AMD Athlon 64X2, 4200+
Mainboard: ASUSTEK M2N4SLI.
Memory: 4Gb DDR2 Dual channel 200Mhz
Graphics: NVIDIA GeForce 8400GS, 512Mb onboard RAM.
Network adaptor: NVIDIA nForce Networking controller
Audio:Realtek AC97.
Four damned edits this has taken, told you I am a numpty!

Edited by deleted (Fri 14-Nov-14 19:36:30)

If you don't have a virus problem I would suggest the flush dns procedure maybe it helps. That would reset your ip settings, you need to restart after that. I think you should also take into consideration the fact that the network card may play up. It's good to have all your drivers up to date also.
If everything fails why not save your work and reinstall Windows?
I know there are quite a few things but if you have the time try them.
Good luck

Thank you for the advice sir, unfortunately I have carried out everything that you outline, but to no avail. The fact that this fault is intermittent is frustrating to extreme. Sometimes the older machine is as good as the new, but that does not last for long. As I outlined in my first post, the main problem is the fluctuations in speed and difficulty connecting. Anyway, I shall sleep on it for tonight and persevere in the morning.