Which is the best Windows for my Dell Laptop?

Hi,
Welcome to the forums, create a small partition and try the trial version of Win 8.1 Ent, I couldn't find the Pro version.
Downloads and Free Trials - Microsoft Business UK

Hi, download the windows 8.1 upgrade assistant to verify that your system is compatible with Windows 8.1 Upgrade Assistant: FAQ - Microsoft Windows Help

The minimum specifications from the Microsoft website are as follows:

Windows 8.1

If you want to run Windows 8.1 on your PC, here's what it takes:

• Processor: 1 gigahertz (GHz) or faster with support for PAE, NX, and SSE2 (more info)
• RAM: 1 gigabyte (GB) (32-bit) or 2 GB (64-bit)
• Hard disk space: 16 GB (32-bit) or 20 GB (64-bit)
• Graphics card: Microsoft DirectX 9 graphics device with WDDM driver

This link will give you more information:

System requirements - Microsoft Windows


Windows 7 system requirements


If you want to run Windows 7 on your PC, here's what it takes:
[FONT=WOL_Reg]

• 1 gigahertz (GHz) or faster 32-bit (x86) or 64-bit (x64) processor
• 1 gigabyte (GB) RAM (32-bit) or 2 GB RAM (64-bit)
• 16 GB available hard disk space (32-bit) or 20 GB (64-bit)
• DirectX 9 graphics device with WDDM 1.0 or higher driver

[/FONT]
More information:

Windows 7 system requirements - Microsoft Windows


I agree with Werty have a look at the upgrade assistant for Windows 8.1 will give you a good overview of what in your current rig is or potentially not compatible.

Cheers,
Harry

The Dell Latitude D620 is an older (discontinued) model so I'm guessing you bought it used. Moreover, according to the Intel ARK specs, your CPU is not even capable of running an x64 OS. So why bother?

ARK | Intel® Core? Duo Processor T2400 (2M Cache, 1.83 GHz, 667 MHz FSB)

hi
i dont think so that is a good idea because windows has internet drops so idont think thats a good idea

The short answer is, whichever fits your needs. Now if you are not using any hardware or software, that cannot run on say Linux, then you are stuck with Windows. There is also Xubuntu 12.04 LTS, if you want something light & easy, along with fast. As for switching to 8.1, I would say to just stick with 7.

Windows 7 will do everything you need, and unless you need Work Spaces or Storage Spaces, there is no need to move into 8.x.

What ever you do, your going to want to make your recovery media, if you haven't already. If you try 8 and don't like it, you'll want some way to go back to 7. The only trial I know of is the Enterprise trial which would be very similar to 8 Pro. It likely has all of its features and then some. Download Windows 8.1 Enterprise Evaluation