Hello!

I have an older Lenovo laptop model N100

Specifications

Model: N100 0768-21U
CPU: Intel Core Duo 1.83GHz T2400
Chipset: Intel 945 Express
Memory: 1024MB DDR2 P5300(up to 2048MB)
Hard Drive: 100GB Hitachi(HTS541010G9SA00) SATA(up to ? 320GB? - i am not sure)
Screen: 15.4" WSXGA+ 1680x1050 Glossy
Optical Drive: LG GMA-4082N DVD-/+R/-RAM

GPU: 128MB Nvidia 7300 Go

It is rarely used, but still work fine, so i am planning to use this laptop for some presentation(videos,LO Impress presentations, etc.)

Which distro is the best for this?(mainly for presentations)

I don't think which distro has a helluvalot to do with it, personally. It will behoove you, however, to go with a minimal or base install of a distro that has has either no DE or a light one up to XFCE as the heaviest.

I would lean towards a Debian-based but a Slackware-based distro like Salix xfce would work fine if you do not mind trading a little work for customizability; debian, on the othe hand has huge reposoitories from which to choose apps. I'd look at antiX-M11 (download base install here) because it is snappy on almost any old PC or laptop and has a great support team (as does salix).