Programs Launch Slow After Reboot

I'm cleaning/tuning up a friend's pc and, after rebooting, programs are slow to open--Firefox, IE, any program in Programs List, etc. Once I've clicked on one and wait for it to open, it closes normally. After opening/closing a few, then the pc starts opening/closing progs. better, but not acceptable. However, once opened, using them is a wait and see (hesitations, browser pages taking forever to display and change, typing in Word hesitates, navigation in programs is "stuttery", etc.) Bootup and shutdown times are acceptable. Below are some of the things that I've done to try to solve this problem:

Auslogics--defragged & optimized
ran Windows Disk Cleanup
ran Error Checking on c:\--all OK
ran Malwarebytes, Spybot S&D, Superantispyware, Ccleaner--all OK now
ran Avast full system scan and boot time scan--OK
turned of all startup entries except Avast with Ccleaner
turned of all unneeded services via services.msc at blackviper.com
Sysinternals Process Explorer with the larger values shows:
Avast Service--103,468KB
Avast Antivirus--272,876KB
Firefox--272,876KB
Task Manager shows:
no unusual processes
Commit Charge
Total--576976
Limit--2519648
Peak--630320
I have to admit that I'm as dumb as a box of rocks on the Process Explorer and Task Manager readings, but in my research some helpers seem to be interested in these.

I'd greatly appreciate any suggestions that I haven't tried yet. It's probably something simple and obvious, but I can't find out what's causing it. It seems to me that something is running in the background and is causing this behavior. Thanks in advance.

Dell Dimension 2400, 2.4Ghz, 1GB RAM
Windows XP Home Edition SP3
Avast free

 

2GB. I'm aware that more RAM is better, but she's not going to put more $ into it as old as it is--even tho RAM is affordable

 

That Dimension 2400 may not accept more than 1GB of RAM. My Dimension 4500S didn't. I suspect that it's Avast that's causing the slow down. MSSE is still available.

 

Oops, sorry misread your question Dr. There is, indeed, 1GB RAM installed. But I don't remember now where to find how much is available if I'm understanding the question. Be easy on me--I'm somewhat "green" on these things. lol
Hard drive is 37.2GB total and 25.2GB free

 

Duh, thanks for joggin' my memory dr.
Physical Memory (K)
total--1046528
Available--530016
System Cache==513284

 

Part of the issue could be that the cleanup method resulted in removing the contents of the Windows Prefetch folder, that should repopulate with more use. I don't recall if XP has a specific Service for that, Vista and onwards does (SysMain/Superfetch).

Old and unused files can safely be removed from there (the CCleaner method is fine), the remainder will enable faster program opening and better file placement during defrag for a (slightly) quicker boot up.

 

Superfetch wasn't available in XP.