Lets start with a little bit of background:
Max memory can be limited by many things, including the motherboard and the memory controller (which these days is part of cour CPU). These parts of your computer may happily work with 8GiB or even more.
Another limit is in the OS. A 32 bits OS usually counts from 0 up to 232. That is 4GiB.
There are tricks around this, think of the 4GiB as a A4 sized paper with limit space on it. Of you could turn pages and use multiple A4 paper you could use more. In computer terms that required PAE (physical address extension) and sufficient address lines from the memory controller to the memory on the motherboard.
PAE had some drawbacks and allmost all CPUs from the last 10-15 years support 64 bit mode, so we are not using it anymore. That means that as of windows 7 you have two choices:
- 32bit OS. Max 4GiB (min address space, preferably a lot less so you can use ASR).
- 64 bits OS. No drawback unless you have very little memory. Future proof. The stuff that just about everyone uses. Really should always be used if you have over 3GiB. (3.2/3.4GiB is usually most max usable by a 32bit OS, with PCI config space, memory mapped graphics etc using the rest of the address space).
later I come to know that 32 Bit computer can't have more than 4GB RAM, even if you increase the RAM in another slot that wont be used.
Close, but no cigar. the computer (hardware) can handle it just fine. Often an OS can to (e.g. any GNU/Linux install with PAE enabled in the kernel. Win XP could.
1 Can 32 Bit be enhanced to 64 bit. Is that possible?
Yes, but there is no clean upgrade path for windows. You will need to make a backup of your data (or if you already have a backup, check that it is up to date and working) and then do a clean install of win7 x64.
If yes then How should I check to see If my computer can be upgraded to 64 bits. Is there any utility or software that can tell me If I can upgrade to Window 7 - 64 bit?
Some things you can check for yourself though, like if you have a 64 bit capable CPU. The short answer is that you have one. See ark.intel.com.
Other than that the upgrade itself will not start of your system does not meed prerequisites.
32 bit to 64 bit upgrade will be chargeable?
Usually not. The same COA (key) is legally usable for 32 and 64 bit windows as of win 7 and onward. There are some exceptions (e.g. some OEM ship their system with 32 bits OS and a key which only works for 32bits installs. Lenovo/IBM is an OEM, so this might apply).
An original window was provided at the time of purchase. Do I just need to save the Key and the re-install window and they when it asks for Key i just put the Key or I will need some thing more to License the > window in a fresh installations?
Saving the key might need an external program to actually get and view the key (hint: it is not a code which is shown in plain text by windows).
However starting anew with windows 7 might not be the best time anymore. Support is running out and after installing your system will need weeks to get all updates. It might be worth downloading a winows 10 x64 ISO and trying if that works on your system.
As to put this into some perspective:
Windows 7 mainstream support ended on the 13 of January 2015.
It is still in extended support up to the 14th of January 2020, but already things are showing signs of lack of support. E.g. windows update running forever at 100% CPU time. Windows update from a clean SP1 install taking over 12 days, followed by more reboots and updates. Microsoft really want to kill this OS.
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