I have been gifted an old but working Dell Inspiron 5100 with a Pentium 4 proc and a 40GB hard drive. I was wondering what upgrades I could do to make this more functional. For example, adding more RAM, but I don’t know what type it uses. It is from around 2003-2003. If possible I would like some recommendations, also want to know if I could OC it a little for a speed boost.
You're not really going to be able to do much. I would max out the Ram. It looks like according to Dell's website this RAM is what is used an is compatible with your model laptop http://accessories.us.dell.com/sna/productdetail.aspx?c.... I would also trash the measly 40 gig HDD and replace it with with atleast a 320 Gig HDD but I would go for 500 Gigs.
you could check dells site using the pcs service tag, assuming it is still readable and check product specs to see motherboard max ram and type, but its probably 128 pin pc100 or pc133.
RAM system max is probably 500MB, as most laptops didn't have many slots back then and mobos didn't recognize much.
As mouse pointed out, there's not much you can do.. most laptops you can only really upgrade ram, hdd, and software.
it might be best used as a specific use like mouse said, maybe a dedicated game server or browsing machine. If you want to use it for basic internet / chatting / word processing, you may want to consider using a linux distro which is made for old hardware. They can be small install and use low system resources.
I am no expert on linux distro's at all. but it can't hurt to give mint a try... ubuntu was supposed to be the most compatible one might want to take a look at puppy linux, pretty sure I used that on an old athlon 3400.