There’s non-zero (althought very small) possibility, that’s it’s avast’s own scan string which got swapped there. Or it may be also string from other antivirus.

2) Why does avast list pagefile.sys among its default "excludes" in the software's "Standard Shield"? ???

Because viruses can’t reside there, the file is usually large and is susceptible to such a false alarms.

3) By deleting the pagefile.sys file, have I lost something critical to my system's performance? ???

Yeah, you’ve lost performance :wink: But most probably windows re-created the file again.

See here for swap-file explanation: http://searchwin2000.techtarget.com/sDefinition/0,,sid1_gci213077,00.html

For the others: Don’t do this at home! ;D