Is this a 32-bit only CPU, or does it have 64-bit capabilities? My Dell D630 is a Core 2 duo with 64-bit capabilities. I run a clone of Red Hat Enterprise Linux (Scientific Linux) on it very nicely. Getting the WiFi working took a little work, but it functions nicely once I got the correct driver and firmware installed.
In any case, a lot of people like Linux Mint, a clone of Ubuntu, which is a clone of Debian. They are more up-to-date kernel-wise than RHEL, CentOS, or Scientific Linux. They also support newer software, such as Google Chrome for a browser (no longer supported on RHEL 6.x systems, though Firefox is fine).
Anyway, my recommendation is that you experiment and find a distribution that you like better than the others. You may need to burn a few live DVD/USB devices (you can reuse the USB thumb drives) and try them out before you find the one that says "ME". For USB live devices, check out Unetbootin. It has software for Windows, Linux, and OSX, though the resulting USB drive, if created on OSX, will not run on an Apple system. Here is a link: http://unetbootin.sourceforge.net/
I have an old laptop from roughly the same generation (similar specs, core 2 duo and 1 GB of RAM), and I run Lubuntu on it, which is a light-weight variant of Ubuntu that works very well for such older hardware. That's what I would recommend for your hardware. There are some variants of Lubuntu too, like Peppermint OS.
There are some other variants that might work too. If you really want to avoid Ubuntu variants (why?), then you could go for the LXDE spin of Fedora, which is kind of the fedora equivalent to Lubuntu.
Lubuntu follows the same support schedule as the main Ubuntu. You can get the latest LTS (Long Term Support) version, which is 14.04, which has official support until 2019.
or i have to update system daily...!
Not sure what you mean. You get automatically notified of any software, OS, or kernel updates available. It is true that they come pretty regularly, almost daily, but that's just because the open-source world is very dynamic and responsive to bug-fixes (and especially security vulnerabilities, if any). Most of the time, you don't have to restart your computer when updates are done. It is really only kernel updates (that come maybe once per month, approximately) that require a reboot. The only reason why it seems that you constantly get updates in Linux is because all the software (applications) updates are channeled through the package manager (software center). By contrast with Windows, Windows updates only Windows itself (kernel and its other bloated OS "frameworks") but does not update any of the applications, which means that you typically just have the version of the applications that you originally installed, with virtually no updates. In Linux, all applications (and the libraries they rely on) get regularly updated, but like I said, most of them don't require a system reboot, all you have to do is click on the icon, approve the updates and go about your business as usual. And if you don't want to bother with updates, just don't install them (or install them later).
IF you don't like Ubuntu you could try Fedora Core which is based on Red Hat instead of Debian. I run Fedora on my laptop and it works with all my hardware (except the finger print scanner) and had drivers for everything else with no special downloads. I would go with the 32 bit version of fedora 20 and try the live CD. With it you can test run fedora 20 from the CD without installing the software over your current system.
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