I am new to SharePoint and I need to install it on standalone system.
Can I do it on Windows XP?
Can I install WSS or MOSS for free?
Please provide me with links so I can go about installation.
You cannot install SharePoint on XP. There is a round about way of installing it on Vista (see http://community.bamboosolutions.com/blogs/bambooteamblog/archive/2008/05/21/how-to-install-windows-sharepoint-services-3-0-sp1-on-vista-x64-x86.aspx) but you should try and install it on Windows Server 2003 or 2008. By doing so you will get Windows SharePoint Services 3.0 free with your server licence. MOSS, or Microsoft Office SharePoint Server 2007 is not free. There are 2 flavours, Standard and Enterprise.
Here's an installation guide to get you going. http://technet.microsoft.com/en-us/library/cc263202.aspx
If thinking about SharePoint 2010, you can install that on Windows 7 or Vista, but needs to be 64bit.
WSS can be installed for free, so can SharePoint Foundation 2010, which should be released tomorrow. You cannot install WSS on XP, it must be a Windows Server 2003 or 2008 server. While SharePoint Foundation 2010 can be installed on Windows 7, this is for development use only, and you will still need to install it for production on a Windows Server 2008 server. It will also need to be 64-bit for 2010. You can find more information here: http://sharepoint2007.microsoft.com/Pages/Default.aspx