How do I upgrade my Z600

Hi,

I bought a Z600 several years ago to future proof myself for a while. I'd now like to upgrade it as much as possible, but have no idea where to start.

I use my PC for website development, graphic design and audio editing.

The PC is getting a bit sluggish, although I do keep the C drive as clean of junk as possible - But do run some pretty intensive programs in my work.

What would the best and easiest upgrades be for someone who doesn't know much about the insides of a computer. I don't really want to be soldeing anything, but do feel comfortable opening it up and doing basic things such as swapping memory etc. I just have no idea what parts this computer needs.

I guess I need memory and perhaps a solid state HD. 
What parts would be suitable?

My partner works for HP and can help me source the parts but would require part numbers. Any help appreciated.

Motherboard:
      CPU Type                                          4x , 2133 MHz
      Motherboard Name                                  Unknown
      Motherboard Chipset                               Unknown
      System Memory                                     6128 MB
      BIOS Type                                         Unknown

CPU Properties:
      CPU Type                                          4x 
      CPUID CPU Name                                    Intel(R) Xeon(R) CPU E5506 @ 2.13GHz
      CPUID Revision                                    000106A5h

CPU Speed:
      CPU Clock                                         2129.39 MHz  (original: 2133 MHz)

Physical Memory:
      Total                                             6127 MB
      Used                                              4371 MB
      Free                                              1755 MB
      Utilization                                       71 %

    Swap Space:
      Total                                             9795 MB
      Used                                              6168 MB
      Free                                              3627 MB
      Utilization                                       63 %

    Virtual Memory:
      Total                                             15923 MB
      Used                                              10540 MB
      Free                                              5382 MB
      Utilization                                       66 %

    Physical Address Extension (PAE):
      Supported by Operating System                     Yes
      Supported by CPU                                  Yes
      Active                                            Yes