CS5 suddenly slowed right down on PC Windows 7

Question

Hi,  my CS5 Illustrator, Photoshop & Bridge have suddenly slowed right down just in the last 3 or so weeks.
Even a diagosis of my PC says it is running very slowly, so I read up on the trouble shooting advice, updated the graphics card driver that was the only thing out of date, did disc cleanups, deleted or moved a lot of big files to other drives, defragged, but still no improvement.
I used to be able to open 300 mb files, but now just opening a 8mb file leaves my PC hanging, for about 10 mins.
These are my specs, & Norton's analysis. Even though Norton says my Windows Firewall is dsabled (because I have a different firewall), it says 0 virus problems. What else could be happening?
HP Pro 3130 Small Form Factor PC, running Windows 7
4.00 GB RAM
32-bit operating system
4 processor cores
64-bit capable
3414 GB hard disks
Disk partition (C:) 114 GB Free (460 GB Total)
Disk partition (D:) 936 MB Free (6 GB Total)
ATI Radeon HD 4550  Total available graphics memory 1899 MB
Dedicated graphics memory 512 MB
Dedicated system memory 0 MB
Shared system memory 1387 MB
Display adapter driver version 8.940.11.0
DirectX version 10

Answer 1

And you're trusting Norton on this, right? Sorry, but to be blunt: That's like fighting fire with gasoline. In fact Norton's tools have long been known to be as conspicuous and overly agressive as some computer viruses themselves. For all I know, it could be their bloated services, virus vaulting and endless scans at the most inconvenient times that drag down your system. Or conversely you do have a virus and Norton is constantly battling it. The long and short answer therefore is: Nuke your system, reinstall it from scratch.
Mylenium