I have 64 MB Ram

Well, the discrepency is too small to be due to onboard gfx or something of the sort, but 2 possibilities. There's an estimate being made wrt your memory modules, and the actual memory isn't an exact value. Or perhaps when the system POSTs, all the memory isn't checking OK, and therefore it only reports what the BIOS found to be good, upon a system diagnostic. Hopefully it's not the second possibility, as when memory starts to go bad, it doesn't just end there...

How much RAM is being reported by the BIOS itself, when you enter system setup? Upon booting, depending on the motherboard and BIOS, it could be the DEL key, the F1 key, or the F2 key. If you're not sure, try them all, when you first turn your machine on, and before it goes to load anything... If it reports the value in KB, just divide the number by 1,024 (and note it's 1,024 or 2 ^ 10, and not 1,000) to get the actual value in MB

It might come up, or there might be some option for system info or the like. Does that report 64 MB, or some other value?

Honestly though, without knowing what system your running, or anything about your computer, it would be hard to say why this is occuring. Perhaps doubling your RAM to 128 MB wouldn't hurt, if it's new enough that you can still buy memory modules that it will take. Good news there, memory has become rather cheap, compared to what it used to be. I just recently got 1 GB of Corsair XMS Pro 400, at about $142, albeit there was a sale at Best Buy at the time which had it at 50% off...

While these are all possiblities, there is one thing that is not mentioned that affects all computers and causes almost every computer that nominally has 64mb to not actually have 64mb. There are several sections of memory that are reserved for various BIOS and administrative purposes. Most notably the block between 640k and 1m is reserved for boot ROM.

The projects generally set the limit to 64*2^10 exactly, or 65536 bytes. So if any byte is not available there will not be enough memory for the project.

Let's not kid ourselves - 64MB of RAM isn't enough for any post-Win98 OS to operate itself correctly (without hammering the swap file), let alone anything else!
My first (2000) PC was WinME, 64MB RAM, and I almost wrote a thank-you note to the person who stole it 5 months later, except that I'd just the week before added a 256MB stick that allowed it work as it was mis-designed to do.