Install and use an antivirus tool. I expect you are but make sure it's up to date and running all the time.
Having that stuff running constantly in the background can slow down a computer, even bring a slower machine to it's knees.
Kill the craplets. Dump things like quicktime, scanners, cameras, music services, If you uncheck anything critical you can always reset the check mark and reboot.
That'll make a huge diffence, and free up a lot of memory and system resources.
The windows firewall is not particularly good. For simplicity, Zonealarm is good and available in a free version.
That's a great program, one of the few things I allow to run constantly. Once installed, you can disable the Windows XP (that's your operating system?) firewall.
install ubuntu linux for free-
There are so many computer functions not available to Linux, but it's fun to play with if you're so inclined. I would recommend adding a second hard drive ($44) and setting up a dual-boot system. It's easier than it sounds, and that method would not require any changes at all to your current drive's partitions.
We have an old .5G of mem, 2.5 GHz pentium 4 that's a bit sluggish bringing up applications. At work I got a new duo core, 2G of mem machine that's much faster. Now I want to upgrade the home machine.
It is worth adding memory with that processor, to speed it up. Or should we just get a new machine?
Our use is pretty much limited to browsing, word processing, etc. No gaming to speak of.
I expect the primary difference between the two computers is the processor. You can check out the CPU comparison charts at Tom's Hardware to see the performance differences side-by-side.
Something else that makes a great difference, having real sound and graphics cards instead of the onboard/integrated junk. Other things are the hard drive, motherboard FSB, graphic settings, and amount of peripherals attached.
If the main issue is programs being slow to start, I think that is something that more memory might improve. I run 2GB on my own computer, and just recommended 1GB to some folks who have similar computer needs as you.
Keep in mind that with most modern motherboards, the memory will perform best if installed in matched pairs.
But you might be able to 'fix' the computer you have first, without actually installing any new memory. The amount of applications and drivers loaded at boot, the number of programs running in the background, bloated cache temp and backup folders, etc. If you haven't reformatted the hard drive and reinstalled Windows lately, your computer simply isn't running like did when new.
I just made a quicky parts price list for my partents-in-laws who are considering a new computer. They have the same computing needs as you, and are ~really~ tight. I came up with $486 to build a new computer re-using their existing monitor, keyboard, printer, etc. I can post or e-mail the specs if you're interested.
My own computer was $2000 for parts, but I admit to going overboard.
