How much RAM is required by Windows XP to operate ?

I know XP works in as little as 256 MB, and I believe even less although it would be very slow.  Windows 7 minimum RAM requirements are 1 GB for 32 bit and 2 GB for 64 bit.  It is slow in 1 GB, so you'd be better of with 2 GB even for the 32 bit version though.

 I hope this helps.  Good luck.

XP requires a minimum of 128MB of RAM, but realistically you should have at least 512MB.

Windows 7 32 bit requires a minimum of 1GB of RAM.

Can My Computer Run Windows 7?

The basic system requirements are listed below.  Some features have additional requirements.

• 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

Run Windows Upgrade Advisor - it scans your PC for potential issues with your hardware, devices, and installed programs, recommends what to do before you upgrade, and whether you can install the 32 or 64 bit version of Windows 7.

http://windows.microsoft.com/en-US/windows/downloads/upgrade-advisor

Windows 7 Custom Clean Install Steps 

Times to use:

Moving from XP to 7, or unsupported in place upgrade paths (ex: Vista Home to 7 Pro)

Moving from a 32 bit Windows system to a 64 bit system, or changing languages

Don't want to do an in place upgrade, or you want a fresh/clean install

You can use an Upgrade or Full Windows 7 disk to do a custom clean install. This will remove all your programs, but you can save your files and settings to external storage before doing so. You will have to reinstall all your programs after installing Windows 7. Here are the steps:

1. Run Windows Upgrade Advisor - it scans your PC for potential issues with your hardware, devices, and installed programs, recommends what to do before you upgrade, and whether you can install the 32 or 64 bit version of Windows 7.

http://windows.microsoft.com/en-US/windows/downloads/upgrade-advisor

2. Backup all your files and settings to avoid losing docs, photos, and other information. Windows Easy Transfer is a free tool to copy files (not programs) from your PC, and then transfer them back after you install Windows 7. If you don't want to use Windows Easy Transfer, you can copy your files to a USB drive, or CD/DVD. Note: Easy Transfer will not work when changing languages, or when going from 64 bit to 32 bit (it will work going from 32 bit to 64 bit).

http://windows.microsoft.com/windows-easy-transfer

3. Locate the installation disks and any associated product/license keys for all your programs because you'll need to manually reinstall all programs. If you downloaded some programs from the Internet you can redownload them.
4. Put the Windows 7 disk into your DVD drive. A window should pop up starting the install process, when asked the type of installation do you want click Custom (advanced). Note: 32 to 64 bit requires you to restart and boot from the DVD.
5. After Windows 7 is installed you can use Windows Easy Transfer (or another backup method you used) to restore your files & settings, and use your installation disks to reinstall all your programs. Then you're done - enjoy Windows 7.

How To Install Windows 7: 

If you have XP:

http://windows.microsoft.com/en-us/windows7/help/upgrading-from-windows-xp-to-windows-7