A closer look
On the sticker you find the rated timings, capacity and product name. What I do miss here is a suggested operating voltage. Apparently this information has been removed in later revision of the memory, because our friends at Techgage show the memory sticker having that info.
Like most other memory manufacturers, Mushkin uses Brainpower PCBs for their memory.
The bumpy road to 4 GBUnfortunately using 4 GB of main of memory is not as easy as it seems. After installing the memory, the BIOS may only recognize around 3 GB of it. This is because the PCI and PCI-Express devices claim memory ranges in the address space of 4 GB. A way around this is to enable the "memory remap" feature in the BIOS. Then the BIOS will correctly detect all the installed memory. The problem here is that your motherboard may not have this option in the BIOS, so you would lose access to 1 GB of memory.
The next problem would be your operating system. If you want to use 4 GB with Windows XP (all 32-bit versions), you are out of luck. Even with PAE Windows XP can only support 4 GB of memory. Since the PCI devices will need some address space to live at, you will usually lose about a gig of memory here as well. This means that using any 32-bit Windows XP version you are stuck with a maximum of 3 GB of addressable physical memory.
The next problem are 32-bit applications, they can only use 2 GB of memory for themselves, because the 4 GB address space is split into two parts of 2 GB each. 2 GB go to the kernel, 2 GB to the currently running application. So even if you had 32 GB of memory available in Windows, each single application could only allocate 2 GB for its own use. When you pass /3GB to the kernel on bootup, it changes the 2 GB / 2 GB split to 1 GB for the kernel and 3 GB for the applications. However, applications can only use all 3 GB if they have the LARGE_ADDRESS_AWARE flag set in the PE header of their executable. So using /3GB will not magically make all your applications have 3 GB at their disposal. You can manually enable this flag using a Hex Editor or the imagecfg.exe tool which is included with some Windows Resource Kits. Please note that the version you find on Google is from NT 4.0 and does not support changing the flag (it doesn't support the -l command line parameter).
The same applies to Windows Vista 32-bit, the memory split is the same, it's the way 32-bit applications work.
All this can be fixed by installing a 64-bit operating system like Windows XP Pro 64-bit or Vista 64-bit. Now all your 64-bit native applications can address the whole memory, but 32-bit applications will still have the 2 GB / 2 GB split (or 1 GB / 3 GB when used with /3GB).
The drawbacks of using 64-bit Windows are that the lack of application and driver support may limit what you want to do. Also you can not install unsigned drivers on Vista 64-bit, which means that most enthusiast written applications that talk to hardware will not work. (Shawn sent a link to Vista Boot Pro which, among other things, allows you to run unsigned drivers on 64-bit).
Of course if you use your computer in a workstation-like environment with 64-bit applications or Linux (32-bit and 64-bit) you will fully benefit from the installed memory.