A complete list of all your system components (so we know what you have already) and how much you are looking to spend (so we know what to recommend) and where abouts you live (so we know what links to give) and what store you most shop from (amazon newegg tigerdirect microcenter? would help give the best advice
Maybe you could say
processor (e.g. pentium 4, ...)
operating system (e.g. xp 32-bit or vista64 or ..)
disk (e.g. 500 gb, sata)
power supply wattage and brand
pc form factor (slim, mid, laptop.. ?)
-or- model name.number
Long loading times: If the OS is XP, then run defrag. If the OS is win7 then that's automatic. How full is disk ? New disk really expensive now -- flooding in Thailand wiped out much manufacturing capbility. Wait 6 months before buying disk if possible.
Memory: 1GB too small and memory is really cheap. Get another 2GB for total of 3 with a 32-bit OS.