タイマーがずれる件について

フレに剛ガロン中にたいまーがずれるといわれたので、ちょっと調べてみました。
下のは笛たいまーのカウント処理時の時間を裏でMHFベンチ動かしながらMHF本体をウィンドウとフルスクリーンを往復して出力したものです。

2009/10/05 04:13:22.156 [188917.1903653640]
2009/10/05 04:13:23.156 [188918.1897387290]
2009/10/05 04:13:24.156 [188919.1915450880]
2009/10/05 04:13:25.156 [188920.1916320900]
2009/10/05 04:13:26.156 [188921.1913779710]
2009/10/05 04:13:27.265 [188922.3015502780]

2009/10/05 04:13:28.265 [188923.3012597570]
2009/10/05 04:13:29.265 [188924.3021383130]
2009/10/05 04:13:30.265 [188925.3030814180]
2009/10/05 04:13:31.265 [188926.3000329370]
2009/10/05 04:13:32.265 [188927.2989848370]
2009/10/05 04:13:33.265 [188928.3009822750]
2009/10/05 04:13:34.265 [188929.2993852310]
2009/10/05 04:13:35.265 [188930.3025420650]
2009/10/05 04:13:36.265 [188931.3027783120]
2009/10/05 04:13:37.265 [188932.2998923620]
2009/10/05 04:13:38.484 [188933.5191947350]

2009/10/05 04:13:39.484 [188934.5194717820]
2009/10/05 04:13:40.484 [188935.5182369040]
2009/10/05 04:13:41.484 [188936.5221190020]
2009/10/05 04:13:42.484 [188937.5179909150]
2009/10/05 04:13:43.484 [188938.5197238610]
2009/10/05 04:13:44.484 [188939.5212454500]
2009/10/05 04:13:45.484 [188940.5174478200]
2009/10/05 04:13:46.484 [188941.5174700100]
2009/10/05 04:13:47.750 [188942.7852313680]

2009/10/05 04:13:48.750 [188943.7851409200]
2009/10/05 04:13:49.750 [188944.7832797110]
2009/10/05 04:13:50.750 [188945.7833206850]
2009/10/05 04:13:51.750 [188946.7896467110]
2009/10/05 04:13:52.750 [188947.7851872290]
(略)
2009/10/05 04:14:08.750 [188963.7847722060]
2009/10/05 04:14:09.750 [188964.7828928800]
2009/10/05 04:14:10.750 [188965.7865147300]
2009/10/05 04:14:11.750 [188966.7829955520]
2009/10/05 04:14:12.765 [188967.8054624220]
2009/10/05 04:14:13.750 [188968.7856093010]

2009/10/05 04:14:14.750 [188969.7895658090]
2009/10/05 04:14:15.750 [188970.7927054060]
2009/10/05 04:14:16.750 [188971.7928245560]
2009/10/05 04:14:17.750 [188972.7827656730]
2009/10/05 04:14:18.750 [188973.7827083900]
2009/10/05 04:14:19.765 [188974.7988120520]

2009/10/05 04:14:20.765 [188975.8025006880]
2009/10/05 04:14:21.765 [188976.8009732050]
2009/10/05 04:14:22.765 [188977.8020761470]
(略)
2009/10/05 04:14:29.765 [188984.7985037810]
2009/10/05 04:14:30.765 [188985.8068077120]
2009/10/05 04:14:31.765 [188986.7991175090]
2009/10/05 04:14:32.765 [188987.8057758390]
2009/10/05 04:14:34.015 [188989.0487132800]

2009/10/05 04:14:35.015 [188990.0484505250]
2009/10/05 04:14:36.015 [188991.0574821430]

ぱっと見でも300ミリ秒ずれてる箇所があるので、高負荷時は3秒に一回1秒程度ずれていることになりますね。予想以上に精度が悪かったです。タイマーの処理は精度の確保できる方法に変更しなきゃダメかもですねぇ。
俺も俺も!て人がいたら教えてください。フレはオンボードVistaというチャレンジな環境なので、もうちょい参考になる環境が知りたいです。