On top of that the cached files reached half of the respected 3GB of RAM so I proceeded to clear only what I was authorised to and also cleared the registry which I backed up of course.
The motherboard in the HP could only support 4GB of DDR3 so I ordered 4GB of Kingston 1600mhz RAM to replace the mismatched ones.
The second pc, a Dell which hadn't been used for some time, ran far better than I had expected. It also had a AMD processor, this time with 4GB of DDR2 RAM. Upon further inspection, and a bit of research, it turned out that the motherboard had been maxed out, as it only supported 4GB of RAM and AM3 processors of which the best was installed meaning that improvement would be difficult. Upgrading the hard drive would be wasteful due to the fact that DDR2 RAM and AM3 processors are now generations behind.
The company also uses the Dropbox app and the files to be downloaded were numbering in the thousands, no wonder it felt slow, because when I opened up the Task manager and looked at performance the RAM, hard drive and processor were all being pushed to their limits. Of course once Dropbox had finished downloading it became much more receptive so I cleared the registry and recycling bin, updated the Anti Virus and other applications and then started a whole computer scan which dredged up two threats securing them automatically.
All in all a good days work with only new ram to order for the HP and a lot of money saved for the client.