Don't untick Autoexec.bat or config.sys, etc., Windows needs those to run right. Just stick with the items under the Startup tab and leave the rest items under the other tabs in SCU alone.
You best bet is to choose Normal Startup one time; Restart your computer when prompted, then back at Desktop go back into SCU and just untick the appropriate items under the startup tab, only, this time. Then restart your computer once again when prompted.
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Check your available resources by right-clicking My Computer; clicking Properties; Click the Performance tab. Resources available are displayed as percent there at top. Check it when you get done running the System Configuration Utility mentioned below.
Click the Start button; Run; type 'msconfig', without the quotation marks, in the Run box and click OK; Then click the Startup tab; Uncheck anything you don't need running in the background. For reference on what's not needed running in the background in the System Configuration Utility, view this website first and print out the list:
http://www2.whidbey.net/djdenham/Running_items.htm
It's important that you print out the above mentioned list. The site provides a printer friendly link.
In the System Configuration Utility (SCU), you can uncheck programs you suspect one at a time and restart your computer. If something doesn't work right, you can always go back into the SCU and re-check it and restart your computer via the Start button. The changes are completely reversible by re-checking an item in SCU or by selecting Normal Startup under the General tab in the SCU and all the programs listed run when Windows starts as it was before you started.
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I apologise for stating something you already know.
